You could do a stop-over
flight but its taking a risk that it will take longer to process the application then your stay is. When i got my visa i applied on wednesday, got an email the following day saying it was sent to ottawa and on friday they said it was approved. On monday i recieved it in the mail. The majority of visa's are issued fairly quickly, but you always run the risk if it being delayed for one reason or another.
my best advice, travel to toronto on a holiday of sorts, get your application done, enjoy your stay and plan activities around it, then have them mail you your visa when its fully processed so theres no worry about when its finished. im assuming by stop-over
flight you mean on the way to the
uk, i wouldn't advise it just in case your visa application is rejected, then your stuck with a
uk plane ticket which you would have to have a return
flight with.