You'll be fine. It's not particularly difficult to get in. I had a couple of seneca college friends that got in with terrible high school marks (70s)...although they had a college diploma with ~3.0 GPA. This was back in 2011 though so bit outdated. One of them got into Manchester and the other at Sunderland.
With averages like that i'd just stay in Canada if i were you. Look into Waterloo's "CAP" program. Or just do a couple of years of undergrad and apply in Canadian schools. If you're returning to Canada/states it'll take you at least~1-2 years of licensing exams/intern hours + extra headache i.e. you won't really save time by going to the UK.