I'm not from the UK and I don't think he has done well. This is mostly because his stance that everything will become great when he takes over negotiations is a trump like proposal which shouldnt convince anyone. He's treating the situation with the EU like it's a game of chess and he's simply the better player than May. The deal is on the table and there's no way that he'll get a more rosy version and some ideas spouted by some of his followers like the "The EU is scared of a socialist Britain hence why we would get a better deal" are just laughable.
Having said that, Labours position is simply horrible and no one has yet to offer a clear way that they should've picked. In my opinion they should've strongly pushed for a Customs Union deal position from the beginning with an option of a 2nd referendum specifying what "the public wants" (god that sounds dumb). I think with a homogenous party position and proper narrative setting that could've been a genuine way out for them. But that's easier said than done in hindsight. Now, they're in a shit position, everything he would do right now would piss off a lot of people.
And he's additionally not being helped with all the ludicrous shit that's being thrown at him, in the media and elsewhere. You just have to look through the last few pages to see the pathetic "Can't be trusted with the economy" "Terrorist supporter" agenda.
Maybe the tory supporter in here who spout those "Any other opposition would be miles ahead" nonsense should take a deep look at the party they've supported for decades. If it weren't for his referendum call, Paul the Wolf, Sassy Collins, Honest John and whatever they're all named would glorify a leader like Cameron yet he and his party are ten times more responsible for this mess than Labour and that is not because of the referendum call itself but because they've pushed their "business friendly, lets turn the UK into a tax heaven while pushing austerity" agenda for years, feeding the public continuously with fears of immigration and consolidating the beliefs of little Englanders that the Great British Empire deserves something better than the EU.
Yet Corbyn is solely responsible because he doesn't want to join a half arsed talk with May who ignored all the other parties for the last two years and now desperately tries to play the bipartisan card.