Royal Airlines operated on behalf of Travel Pack (who incidentally are still around) they now sell seats on scheduled carriers these days. This must have been in the mid 90's at a guess? They flew to pretty much all the major Canadian cities including Toronto, Vancouver, Montreal. If I remember right however it was a slot issue at LGW and the entire programme was shifted over to STN.
Air Transat were around with their Tristar for sometime previous to this before it was downgraded to a 757 operating to Toronto via Exeter. I think most of the UK regional routes were dropped when they ditched their 757's if anyone can work that one out?
I'm preety sure some of the other Canadian charter carriers used Stansted in the 80's.
Certainly wouldn't go a miss to see Canada back on the departure boards. But if a blood bath emerges at LGW next summer, I personally think I'd see one of the carriers ditching 'London' all together rather than just moving their London arrival point. Shame not to have given it a go mind.