Bob,
no problems with registering a car of that age, mine was probably the 'worst case' no docs, no import papers,etc , obviously if you have documentation then an age related number will be gained rather than a Q ,( unless you have the special offer £250 secret handshake with the DVLA !!! ) These cars look 60's but are made much later than you think.
However have you heard this or is it an Urban myth ?,,,, a man tried to import 5 trabbies into the UK,DVLA turned them down because of the smokey nature of the two stroke engine . more likely they weren't 'personal imports'