I gather you have looked at the exchange rates, but have you checked into the cost of living? While Canada is more expensive than the US, it should be much less expensive than the UK. Canadians I've met who have lived in the UK talk about how much more expensive it is.

I just looked at a book that was published in March of this year. The price in the US was USD25, in Canada it was CND30, and having bought a lot of books published in the UK the last year, I'm pretty sure the UK price would be around GBP25 (or USD50, CND60). I'm told that restaurant meals work about the same way. A meal that would be GBP50 would cost USD25 in a similar restaurant here. Since you are getting more that half of your UK salary, you are probably getting a bit of a raise.