I usually go through T5 at LHR, and every time in the last dozen times I've been there my bag always beats me to the carousel, no matter if I'm in Y, J or F.
I use fast track everything and at worst if it's a bus gate it's about 15-20 min from deplaning through passport control to bag pickup. Last time was maybe 10 min, I basically didn't have to stop walking anywhere and my bag was there before me. It was an evening flight from MUC and the airport was quiet.