"
Wonder what the headstone will record as it is not clear how many actual remains have been found."
Depends if the experts can identify bones from all of the crew members or just some, or if no positive ID is possible. Despite what TV drama's suggest it is not always easy to link small bone fragments to named individuals many years after the event, particularly if they are damaged or burnt.
If no positive ID is possible I believe the remains will be buried as "
remains of the crew of Lancaster ED427" under a single headstone. If all the remains are linked to one or two crew members (disappointing for those relatives where no remains of their loved one are found) they will be buried as the individuals concerned, but in the best scenario, remains of all crew members will be positively identified even if only one or two bones, then I believe all are given an individual headstone even if buried in a single coffin. The MoD / RAF did something along these lines in Malaysia earier this year for the crew & pax of Dakota KN630.
Dakota Crash
Coverage also in the Telegraph
Bodies of five British airmen from Second World War found - Telegraph