If you are a Canadian citizen, you do *not* need a visa to visit UK. If you are a Chinese citizen, you DO need a visa. Here is the link that may be helpful:
http://www.ukvisas.gov.uk/en/doineedvisa/
In April when I go to UK, I had to submit the application form on-line and went over to Vancouver to get the fingerprints gathered.
Cheers,
