I am planning and will be booking this trip a long way in advance (and I know I'll have to, to MFU from WT+)

London->Vancouver, Toronto->London, with stays of a week or so in Vancouver and Toronto

I'd be booking this almost certainly when there is a sale on, whats the recommended booking , I could do open jaw, or multi-city and include the Vancouver-Toronto leg, I'd obviously need a stopover in Toronto though and obviously BA and AFAIK and none of its partners, do Vancouver-Toronto.

Alternatively, if there was a possibility of a big saving, I could do London-Toronto return and buy a seperate Toronto-Vancouver return but then I might have to stop overnight in Toronto outbound, plus more hassle and a longer trip to Vancouver.

I do have the flexibility to swap Vancouver and Toronto around.

Any thoughts?