Steve, pick a place and culture that interests you. How do I put this positively? Study abroad, especially for one semester, is less about the classes and the academic experience, and a lot more about travel, socializing, parties, and experiencing life. I was extremely focused on academics during college, but I still found that my 8 months in Germany were not academically challenging. The professors have lower expectations for the foreigners and it seemed like most Erasmus students were getting their degrees in partying.
Only you will know what's best for you, but go somewhere for the city, culture, people, food, etc., not for the classes, would be my only advice.
My other strictly personal opinion is that the UK is not interesting. The food isn't good. The underlying culture is Anglophone just like your part of Canada. It just won't be as foreign and challenging and adventurous as a place that's not Anglo. Paris is an amazing city. Vienna too. Amsterdam too. The guys in all those places are waaaay hotter than in the UK.
If you want to enjoy gay life, go to a big city. I was in a city of 150,000 for my 8 months in Germany. There were no gay bars or clubs. One of the few ways to meet guys was the Internet, which is not ideal.
But, yeah, go where you want and where you feel the experience will be magical. Good luck!!!