Like mentioned and as you've said yourself, OP, stay away from the cities and you'll be fine. The countryside and it's villages are lovely.
Get used to narrow roads and parking spaces as well as much smaller buildings to live and shop in. There's also far smaller choices of products to choose from when shopping over here as well, not that it's always a bad thing, sometimes it makes things easier.
Take out a mortgage or loan before you plan on re-fuelling your car. It's currently 25-30p per litre less than it was a couple of years ago, but that's still more than £1.10 per litre of fuel.
Don't even think about jumping a queue or people will want you deported.
People's accents can drastically change, even if you just took a 20 minute drive to somewhere else. It might take a little getting used to, some accents are harder to understand than others.
Over all you probably won't feel things are really all that different, just expect everything to be smaller and more cramped.
Edit: Don't know how I left this out. Some of the cities can be useful - they have been filling up with gorgeous Eastern European women.
Smaller roads yes... hilariously narrower at times... but since most people in the UK aren't driving RAM 1500s... it isn't a problem outside of there being actual traffic.
Smaller buildings to shop and live in? Maybe, depending... but plenty of Canadians live in small affordable housing. In fact, houses in major cities are smaller in general than in places like greater Calgary where I live. Apartments complexes, duplexes, and townhouses make up a majority of Canadian homes.
Smaller shops? Not at all... it's just different. North America generally has malls and strip malls, they don't have tightly packed town centers.. but store sizes aren't that different. JD Sports and Sports Chek are roughly the same size, as are grocery stores, tech stores etc.. it really isn't that different.
The point to make about choice of products is patently false. Canada is a very strange place in that there is supposed to be a free market but it's bullshit. The country is super protectionist and whatever Canadian products exist they are heavily prioritized over imported competition.
Amazon.ca is horrendous, and the availability of specialist items such as camera filters for example, is pathetic. I am constantly having to import from the US because they're impossible to find locally. I never had anything close to this kind of trouble in the UK.
Gas/petrol prices also aren't that comparable. People in Canada typically travel far greater distances and drive vehicles that are far less fuel efficient. It isn't a 1-to-1 comparison. Alberta alone would accommodate the entire landmass of the United Kingdom more than 3 times. Canada is insanely vast and even the people that live here don't seem to be able to comprehend it.
Everything else you said is 100% accurate though.
I moved out to Calgary from Manchester 8 years ago for work. I am eligible but haven't applied for Canadian citizenship yet... I will, because it's nice to have options... but I'm not completely sure whether I will stay here long term.
Population density is far FAR lower than in the UK and the weather is infinitely better, even during the winter where some.places have snow on the ground for 4+ months of the year. Wages are higher on average, and I think overall the quality of life is higher, but Canada is significantly lacking in a number of areas, particularly architecture, culture, history, etc.
I always wanted to move abroad. I spent almost 30 years of my life in the UK and while I do appreciate that there are many advantages to living in the UK (the proximity to mainland Europe for example), I haven't yet considered moving back.
I dunno OP, it's a big decision and isn't something you should be fantasising or idealizing about. The UK isn't quaint countryside populated with eccentric warm hearted people. Some remote villages maybe, but for the most part it's grim, dreary, and populated by miserable aggressive people. Better drivers though; the standards in Canada are horrible and places like Calgary and Edmonton provably rank amongst the worst in the world.
The job situation depends on the industry. Before I came to Canada I was applying for jobs that had 400-1000 applicants. The UK is overpopulated and the amount of competition keeps salaries lower than they should be. I teach and make 3x as much now than I could in the UK. I dont know what the job market is like there at the moment but it has to be worse than Canada!?
I can see the appeal though. Most Canadians I know have never been outside of their own borders, some even outside of their own province. I have sturents that come to Calgary from small towns and refer to it as "the big city", yet it's one of the smallest cities I have ever visited. I get the appeal to spend time somewhere far more diverse with a lot more history than Canada. Just temper your expectations.