As has been said, nothing - so long as you’re prepared to wait for the bag. Given the currently reported situation at LHR, with the whole operation short-staffed, I wouldn’t think that was particularly a priority and I could see it taking several hours - all available resource is going to be focused on getting bags through and loaded onto connecting services so they leave as close to time as possible.

The chances are it would be quicker to take the ticketed itinerary and fly onward from there.