Latest update is that the dealers called to say they have been in contact with BMW and told to run some tests....then rang back to say they need to run diagnostic test on it while driving so asked permission for techy to take it home tonight.....fair enough, at least they seem to be trying...still got the Voyager bus from Enterprise which itself needs a service but they haven't found me another option....
Edited to add... having turned up Enterprise depot this morning they magically found me a BMW! Only a boggo 320d...but a lot better than that mobile contraceptive Voyager diesel!!