I believe the Exeter route to Toronto is not operating this summer.
I just checked
Cheap Flights to Canada, Toronto & Vancouver from London & major UK Cities | Air Transat and it does appear to be operating this year and goes via Glasgow operating on a Wednesday...
However at £489 each way, Im not sure I would want to be on a 9 abreast A310 for 8 hours, when I could fly with a scheduled carrier for less and in more comfort!
However saying that, I have flown with them before when I got a bargain return ticket for £250 from Manchester and was very impressed. Very professional, good leg room and the A310 was a pleasant experience, if a little cramped.
I just think its a shame Air Transat didn't think of switching to Bristol as could make a real go of it, with the larger catchment area. Operating to Toronto from Exeter has always seemed a bit of an odd ball to me, but there must be demand I am missing.
Incidentally, the TOM B 767s do fly from BRS to Sanford non-stop nearly all the time, possibly all of the time. Cancun though requires an outbound fuel stop at Manchester.
Nearly fell out of my chair when I read that the Florida service operated non-stop. I bet the tail of that 767 is scraping the end of the runway to get airbourne!
Do they limit the loads on this flight or does it fly out full?
Saying that Monarch did operate their A330 from Luton to Orlando in the early 2000's on behalf of Airtours and they operated non-stop, so anything is possible!