i'm 100% certain that luggage is checked straight through to your domestic UK destination.

over the past five years i have done the following routes -

hkg - fra - lhr
hkg - fra - bhx (birmingham)
hkg - cdg - edi
hkg - lhr - edi
hkg - fco - lhr
hkg - ams - lhr

most of these were reward flights, hence the strange stopover

and on all occasions i have been able to collect my luggage at the destination.

hope it solves your question !