I would simply try to get them to merge the two PNRs. This is made trickier by one being an awards booking, but should still be possible. Been a while since I have flown or done anything with my EB points, but many other airlines will do this.

If you can get the two PNRs merged then it should make getting your luggage checked-in all the way easy as pie. Also it would greatly reduce the time needed to connect in LHR. Please remember though that LHR is being "reshuffled" at the moment. This does mean that the terminals are "under construction", and the same for the lounges at times. Not sure when you're going and whether you have any access to any lounges. Just not sure I'd wanna make the layover to long either for fear of boredom :P