I don't believe 6 days is a realistic waiting time. You should expect at best 2-3 weeks, and realistically 4-8 weeks. If you can travel to Canada visa-free, you still can manage to do it, if you need a visa - just cancel your trip or postpone it.
Transmission fee depends to which VFS you'll send the money to. Fees for VFS London are described here: https://visa.vfsglobal.com/gbr/en/can/additional-services
I am not sure if you can ask the VFS to send your passport to a specific VO for visa-stamping and hence avoid London VO. I know there's nothing directly saying that it's not allowed, but if you're now on the same continent where your VO is, it's very unlikely that VFS will listen to you and not send it to your VO. Your VO is based on your residence country, check it here: https://www.canada.ca/en/immigration-refugees-citizenship/corporate/contact-ircc/offices/find-visa-application-centre.html