By Mark Trevelyan

LYON, France (Reuters) - Robert Fawcett has already cast his postal vote for Britain to leave the European Union, but since arriving in France for the European soccer championship he's suffered moments of doubt.

Mingling with supporters from many countries in the southern French city of Lyon, with the beer flowing freely and the fans singing and dancing in the streets, the 25-year-old engineer from Grimsby, northern England, is feeling a bit more European.

He says his vote to leave the EU - the question on which his fellow Britons will vote on Thursday - was based on the plight of his coastal hometown, depressed by the decline of the fishing industry which many locals blame on EU quotas.

"There's not many jobs available around Grimsby and it is a big thing for me, and that's one of the main reasons I voted out. But it's different when you come to Europe and you see everyone together, you do maybe regret it a little bit."

Among the huge contingent of fans from England, Wales and Northern Ireland at Europe's biggest sporting event, views on Britain's most momentous political decision in a generation are as divided as in the nation as a whole.

At one extreme is the hostility of a small minority, like the England fans who, during several boisterous days in Lille before their match in Wales, chanted: "We’re all voting out/We’re all voting out/F**k off Europe/We’re all voting out”.

But among others interviewed in Lyon before England's match against Slovakia on Monday, attitudes were more thoughtful.

Fawcett's friend Liam Blades, 24, a technician who works at refineries, has arranged a proxy vote to remain in Europe.

"The EU's been around so long and the countries have been together so long, and if one starts going and they all start breaking up there could be friction between the countries, you don't really know what's going to happen," he said.

He pointed out that the Eurostar train that brought them to France took only minutes to zip through the Channel Tunnel, but wondered whether things would be quite so simple if Britain breaks away. "There could be restrictions applied, couldn't there, if we leave the EU, so that's another a big thing."

Jamie Malley, from Arbroath in Scotland, has already voted to stay in Europe. "I feel as European as I do British, to be honest. I don't want to Brexit, I think we should remain."

But his friend Jon Bickley, from Bath in western England, is still hesitating. "We spoke to some Albanians for the first time ever yesterday. Turns out they live in London, but they were still Albanians. I know they're not in the EU, but it does make you feel a bit more European, yes," he said.

"I'm sort of torn at the moment. Possibly with Jamie in my ear for 24 hours a day, I'm getting more 'Remain'."

Opinion polls show Britons almost evenly split ahead of the referendum. Campaigning resumed on Sunday after a three-day hiatus following the killing of a pro-EU lawmaker.

"WE SEEM TO BE HATED"

England fans, labelled for years as trouble-makers because of the behaviour of a violent minority, hit the headlines again this month in France when they clashed with Russian supporters in Marseille.

While most speak of an atmosphere of camaraderie at the tournament, some say they sense hostility towards them, partly because of their reputation.

Plumber Matt Tory, travelling between matches with a group of friends, points to an incident the previous day when their minibus broke down.

"We went and asked the Polish, we asked the French to help us out. They were just walking away, leaving us stranded. So if they want to be one unity and that, they're not going the right way about it, really, are they? People just didn't want to know."

His friend Chris Poulson, 39, puts it more strongly.

"We seem to be a hated nation," he says, blaming this in part on historical factors.

"Obviously we did used to rule, what, three-quarters of the world or whatever it was, years ago. It sort of winds me up, I think, especially with some of these other countries. It's almost as if they look down on us.

"Maybe we're not as cultured as the French and the Italians, they speak different languages and what have you, but we're not stupid people. You know I try, I do try and get past that language barrier and if I go anywhere I try and say please and thank you..."

Still, he plans to vote to remain in Europe because he is worried about his son's future. "That's what I'm thinking about, is when he grows up. It's going to be bad enough as it is, I think, in 10, 15 years time with the way the world's going."

Their friend Mark Kelly says the experience of being in France and mixing with foreign supporters is not really making him feel any more European.

"You talk to them and you have a laugh but it's not about politics, is it, it's about sport at the end of the day...

"I'd say the majority of the English are saying they want to get out, but there's a few that's saying stay in. The thing is, you don't know who to trust, who to believe. You get a bit of crap off everyone."

(Reporting by Mark Trevelyan; Editing by Gareth Jones)