seeing this probably is a tech topic I am posting this info in its own thread here.
After some research I located some MAF sensors that may have been the same as ours but all in theory, nothing proven - until now
.
Having just had a very nervous M5 owning mate watch me strip his MAF, and refit it, I can confirm that the M5 E39 Bosch MAF, p/n 0280217533
, contains an F00C2G2029 insert, same as our cars.
SO,
if this is a genuine Bosch we have a source of new genuine MAF sensors for about £76 including postage.