Thanks for all your helpful suggestions. Seems to me that if the thread size is the same, a set of 27mm D2/P38 nuts should sort it. Failing that, changing the hub studs to standard P38 should allow me to mount the D2 wheels. Can't belief the wheel holes have been enlarged, so it has to be the nuts/studs.
I'm away for a fortnight at the end of the week so won't be doing anything till I get back. I'll report back later.
Cheers All.