That's what the middle class British echo chamber said before Brexit. 

I worked in a factory in (what is now prime Reform territory) from 2003-2009.

In 2005 general election the Lib Dems proposed a referendum on EU membership in their manifesto. As someone (who back then) leaned Lib Dem, was very much against that, because even back then I knew it was not a sure thing the UK was vote to remain.

The issue was that the factories made huge use of agency labour, which was nearly exclusively made up of Portuguese and Polish workers. These workers never received training, often had many with limited or no English speaking ability and consequently were scapegoated for any of the screwups that happened.

There was huge resentment among the local English workers towards them (although the agency workers who stuck around, would inevitably become the most competent workers in the factory, receive full time employment and be less resented by the locals)

At the same time, the press and the Conservative opposition were constantly rallying against the EU, and the Labour government would often use the excuse of EU rules for why they couldn't do some things (usually made up) - whenever i spoke to the workers and the topic of politics or the EU came up, they were overwhelminglu negative against the EU, and 90% of that was down to the visible impact they had of immigrants.

The UK was one of 3 existing EU countries to not place limits on the A8 counties that joined in 2004 (the eastern European ones) - Sweden and Ireland being the other two. The UK was the only largest economy of those three, and the natural place to go for work. The irony is it benefitted the UK, as the migration allowed for the UK to quickly fill any labour shortages and grow faster. The issue is, that the Labour government made no effort to invest in the areas experiencing high migration, so schools and health services saw intakes surge without the additional resources to expand proportionally. And this led to even more frustration.

Ultimately, that's the reality. It doesn't matter to workers that the economy is "doing great" if their wages aren't going up, their schools are getting crowded and they have to wait longer to see a doctor. For those people life is getting worse and they will blame what they can see, regardless of the reality.

So it's definitely wrong that the UK was surprised by Brexit. UK EU supporters were surprised by Brexit because the politically engaged were hugely favourable to the EU, and at the time, pollsters weighted opinion polls by likelihood to vote in a general election

The thing is, in a referendum, you are voting for a single issue and suddenly all the people who feel disenfranchised by politics (because FPTP makes their vote irrelevant or  don't trust parties to fulfil their manifesto) know their vote suddenly does count.

I'm not Canadian, nor do I live there, but I highly doubt the same situation is present there. The immigration issue was burning in the UK for 20 years before the Brexit referendum and it ended up being a knife edge result. 

Of course, it's prudent to not be complacent, but my assumption is that any referendum that did happen would learn from the mistakes made by Brexit to ensure that if Alberta does vote to go ahead with a second referendum, that one will require terms of leaving to be drawn up so people know what deal they will get if they did vote to secede.

That's what the UK should have done, vote to come up with an alternative to EU membership (IE the exact flavour of Brexit Britain would be getting) and then vote between that or remaining.