Flew LHR/PHL 10 days ago in F and missed a connection to South Florida due to PHL being the worst airport in USA for transfers. No further flights that day and I needed to get there, so put on a flight to Orlando and BA picked up a $450 limo bill for a 3 hour drive to get me to my destination the same day. Ground services in PHL are awful but with some persistence and one helpful member of staff, got a good result. Nice one!
And a word of warning, if connecting thru PHL (and only do it if you absolutely have to), even if you only have hand baggage, allow 2 hours at a minimum, 3 would be safer! The place is a disaster!