You are welcome. The fee for RPRF is CA$ 490 per adult applicant. Here is a direct link to the London Visa Office fees website:
http://www.canadainternational.gc.ca/united_kingdom-royaume_uni/visas/fees-frais.aspx?view=d
We have been to Knightsbridge yesterday, I would definitely recommend it. We got an appointment quite quickly (called Monday, appointment on Wednesday), they were very friendly and knew what they were doing (while we were waiting there were about 4 other Canadian Medical Exam applicants there).
Good Luck.
Miki