Thanks all! I'm getting the impression (the last I overheard) they are now seeing some sense and thinking of just going to YVR.
I had searched for the LHR-YHZ and LHR-YYT flights but they came out more/too expensive for their budget.
LHR-YHZ was more expensive than LHR-YVR for the date range they were looking at.
I'll try to shift their focus onto Air Canada as I think AirTransat sounds very uncomfortable, even if they end up just doing the one return journey.