On 3 out of 3 trips coming into LHR T5 internationally, and connecting to another international flight, in the past year my luggage has not made the international connection. In each case there were 8-12 hours in the same terminal for my luggage to be transferred. Each time I made it to my international destination but my luggage didn’t.
Rumour has it that LHR T5 is a black hole for luggage. Luggage system apparently keeps breaking down. BA is the only airline responsible for luggage there as they’re the only airline in the terminal.