ammaartahir, don't notify them by email, use a case-specific query on your visa office's website. If you have moved to another country it is vital that the visa office acknowledges your new address. Have a look around here for the online form for London:
http://www.canadainternational.gc.ca/united_kingdom-royaume_uni/visas/update-how_mettre-comment.aspx?lang=eng#email
Regarding your PCC, wait until visa office contact you. For someone people, who have had med requests, the visa office has said they will accept PCC up to 6 months told, in which case you should have enough time to use your existing ones.
Best of luck,
Wayne.