I sent mine Royal Mail track and trace - mistake! Yes, Royal Mail are quick and you can track and trace it all the way until they shove it on a plane for Canada - then Canada Post take over and do - precisely nothing! Took 2.5 weeks to get from the plane for Canada until it was delivered in Mississauga.
Some ideas here on how to send it:
https://britishexpats.com/wiki/Spou...ion_Forms#How_should_I_send_my_application.3F
Personally, I would strongly recommend FEDEX - they track and trace every steps of the way in both countries as it stays in FEDEX. Take 4 days max to get there as they also seem to have their own customs clearance facilities. About £55 all in.
Do remember that it is a different address for courier deliveries that need to be signed for,