So in that case check your bag through to Manchester - you might have no choice anyway - and scuttle off to get and recheck if there's time (2 hours would likely be enough). If not you can blame BA for the failure to collect because of the delay and there's a high chance they'll courier it down from Manchester, even on a different ticket. Or you may be able to SDC to a later flight to give time. Or if you're lucky you'll be late into Heathrow and they'll not be able to transfer it in time so you can get them to courier it back.

All sorts of ways this could play out, but bottom line 50 minutes is not enough time to do anything at all at Heathrow with a checked bag. It's enough to pass through domestic connections probably, but everything on the inbound has to be bang on time which at that end of the day I wouldn't be banking on.