Hi, guys:
I am here to share my experience. I did A-Level in England, scored AAAB, and finally I end up in UBC. I have also got into KCL, Southampton, SOAS, Queen Mary in the UK. The reason to make the decision was I thought North America have much more opportunities and so on. The reason why Canada is because Canadian Universities consider British based education, no SAT requirement, they do accept A-Levels instead of SAT, and you can even get transfer credits for them. However, the Universities in Canada is four years, and it is true that you will lose all you friends back to England (I know it is really painful), you need a long period to gain new friends. There isn't much different of living in Vancouver, however you still need to face a new environment. Vancouver is not as expensive as London, I think is affordable. For example, lunch for about CAD$10 (5 pounds) you can eat for a really good one. The university life in UBC I think it likes the most of good universities in the world, study is stressful and hard.
Hope this helps.