Re: what days are cheaper
Dug around and just found a couple of seats for $677 July 13 - Aug 12. :D
Waiting until tomorrow MIGHT not be a problem but they certainly wont last until Monday. 677 or even 750 are VERY low for a flight to the UK right smack dab in the middle of high season. Problem for you is you want the kiddos comp'd on the same trip - that'll take time to org.
Anyway, a little horror story when it comes to these discount seats: I once found a ticket YYZ-HKG for $825 (stupidly low price). Made 1 phonecall for 15mins, came back to order...and it was gone.