First time post! I hope this isn't too obvious a question...

My folks are about to fly from PDX (USA) to YVR (Canada) to LGW(UK). The two legs were booked seperately, so they are two seperate itineraries, meaning they're not linked and they'd have to collect and re-check their baggage. Is there some way to get the itineraries 'merged' into one, so the baggage can be checked from PDX to LGW ? Or does it need to be re-checked for customs anyway, making this pointless?

Can they have this done when they check in or do we need to call one of the two airlines?

Thanks!

Pete