Hi, I am also a British student and I'll be studying an MSc in Latin American Studies at Oxford in October.
I was, until a few months ago, very set on going to the US to do a PhD, but I have recently been put off of the idea (mainly) because of what I have read on this forum. There is no doubt that the US system offers more money, better quality facilities, more opportunities, a better education, and probably better prospects. I had to ask myself, however, whether I could hack working 60-70 hours a week for 5-7 years, and whether I really want to put off entering the job market until I am nearly 30 years old. My conclusion was that it was probably better to do a PhD in Britain in 3 years and then build up my experience with a post-doc or two. This will probably limit my employment opportunities in the US, but I think I will still have reasonable opportunities in Britain, Europe and Latin America.
I am not informed on the subject, but is the US or Canada really the best place to study renaissance literature?