Sorry, it's early, so i'm bring thick. Are you on a through ticket or separate res? I think you are in club on longhaul and economy/"euro traveller" on shorthaul. If so, just don't tell checkin about your connection, your bags will be tagged to heathrow where you claim & recheck/do whatever.

If on one itinerary and have a same day connection, you'll need to explain you only want the bags to go as far as London. They're your bags and it's perfectly legitimate to want to store bags.