London is a city in the country of England, which is part of the United Kingdom. Canada is a country. So if you have to choose, I would choose the one that is actually a country - Canada.
I love Canada and do a lot of work up there, but if you are trying to immerse yourself in a different culture, Canada isn't really that. Canada is just the US but clean, a slower speed limit and the metric system. England is actually a bit different.