You are conflating a number of unrelated issues here so I'll address them one at a time.
Throughout my travels over the years in the Middle East (long time ago) there was a frequent topic of conversation when I met people....how could they get over to England to work and get rich. Although wars/fighting have increased recently the desire to get rich in England has always been there. Should imagine the African countries have much the same opinion. Maybe that is why we are the first option for so many. It may also explain why so many migrants don't want to claim asylum in any of the countries they pass through.
Britain, like the US, probably does have a greater draw for migrants than other places, but as we're all they see on the TV, hear on the radio and read in the history books it's hardly surprising. Many of them learn English through their exposure to our globally pervasive culture, why would they not then want to head to a country where they can speak the language rather than heading to one where it's all Greek to them.
We also do little to dispel the illusion that our streets are paved with gold. We are, thankfully, a very charitable nation but this can give the impression that we have more than we know what to do with. I worked for a charity that rebuilt an orphanage and fitted out a school, hospital and fire station in a small Romanian town purely from donations and some of the stuff we had dropped on us astounded me, like 3,000 pairs of brand new Adidas trainers that someone diverted to charity as they felt the company instruction to shred the poor selling line rather than cheapen the brand by dropping the price was amoral. But if big business dumping poor sellers is bad then the NHS donations were sickening, they included glass test tubes, stainless steel surgical equipment and even a fully automated dentists chair and drill set all of which had never been used but all of which had passed it's expiry date. An expiry date that was set to avoid the local NHS trust having their budget reduced this year because they still had items from last years budget in the stores.
We don't do it deliberately, but we do manage to give off the impression that we have much more than we know what to do with and that must look appealing to the poorest of the world. I'll never forget one of the Romanian's who visited us breaking down and crying in the supermarket when she saw the 2 aisles of do food, more goods stacked floor to ceiling than her town saw in one month to feed 200,000 people, I'd met the dogs in her town and they contented themselves with trying to eat people.
Some of them have stated that they don't actually want to claim asylum anywhere, they just want to work here and make money. In one interview some stated they just wanted to be illegal immigrants and work and most of them have someone to contact over here who will provide them with said job, usually someone from their country of origin.
These are economic migrants. Our country already has almost 2 million unemployed and perhaps we should be giving a thought to these people who also need work and are our primary responsibility. We also ought to consider that most illegal immigrants working here are not "on the books" and therefore not paying tax or NI contributions.
Illegal immigrants are by their very nature, not on the books and not paying tax and NI, they get no benefits or housing and have no right to remain facing immediate deportation if they are found. Nobody is letting them in, they smuggle themselves in at very high risk and they forego all rights and protections in doing so for a short term financial gain. We should be targeting the employers to reduce the demand, hitting the desperate people trying to better themselves is never going to remove the demand. Economic migrants do also deserve some sympathy though, they are often horribly exploited and live in dire conditions almost like slaves and if they have children whilst abroad, they find their child is stateless and give them lifelong problems. I have a very good friend in Singapore whose Malay parents were working illegally in Brunei when she was born, as such she is stateless. She eventually managed to get a Malay overseas passport and had settled with her Scottish husband in Singapore but when he died she found herself back in her old situation where Singapore refused her long term permission to stay and Malaysia would only allow her a 6 months visitation so she is still living in limbo.
As the Guardian article states however, 62% of those at Calais are genuine asylum seekers who have a right to claim refuge. The remaining 38% would not get past the form filling stage so are trying to get in illegally and would be turned away if caught.
We have far too many British people living on the streets who cannot get a job or benefits because they have no address and they cannot get an address because they have no money. Who is bothering about these poor souls? Some of their lives are far worse than that of the economic migrants. They do not have money to pay traffickers to travel across Europe. They barely have enough money to eat.
These people have nothing to do with the migrants, they'd certainly not be fruit picking or labouring on building sites even if the migrants were gone, most have major issues with mental health and often drug and alcohol dependence and have tragically fallen through the gaps in our welfare system. We should do more to help them out of their situation but in the majority of cases they are not immediately employable so nobody can be accused of coming over here taking their jobs.
Housing...if migration was 300,000 last year then it's too much for a country this size. The area I live in houses approx. 70,000 people. It's large but hilly so it's not possible to build on much of the land. At that yearly rate of migration we would have to build to house 3x the population of that area.
We should not be looking to allow entry to economic migrants whilst there are so many people here who are so needing of our help. It might also help us to differentiate between different types of migrant if we stopped generalising them as "desperate" when "determined" would be far more appropriate.
The 2,500 or so migrants we are talking about at Calais make up less than 1% of the 300,000 net migration figures you quote for last year. The vast majority of that 300,000 are legally permitted EU migrants who have as much right to apply for a job in the UK as you do in any other EU member state and most arrive with a job and housing sorted, they're not turning up demanding a hand out and a new home. Approximately 13% of the UK population are non-UK born so would at some stage have formed part of one yer's net migration gain and of them, the vast majority are gainfully employed and make a net contribution to the UK in terms of tax and NI and that's before we even look at the skills gap they help to fill in our ageing population that helps keep our schools and the NHS functional.
13% is a pretty normal figure when compared with the rest of the EU, slightly behind Austria, Spain, Sweden and Germany and slightly ahead of the rest. It's certainly not something the country can't handle and can't be compared to building 3 of your small towns new every year, you want to try living somewhere like Singapore where a country no bigger than the Isle of Wight has a population of almost 6 Million and almost 50% of those are foreign migrants who are wither brought in for their high skill levels or to do the general labour work in building the infrastructure and keeping the country running.
Personally I'd grant the asylum seekers right to apply and hear their cases in the proper system rather than trying to pretend they aren't there and hoping the French will take care of them, we're doing far less than the rest of Europe in dealing with a humanitarian crisis that our own foreign policies helped create and frankly it's embarassing having a
desperate huddled mass shivering on our doorstep. For the economic migrants assess their skills and see if they fit a need in the job market. I'd far rather a
determined young workforce proudly helping improve the country and contributing to taxes and NI whilst doing so than have them
desperately huddled in poor employer sourced accommodation whilst they are exploited for illegal gain.