Don't agree with the "terrible design" I think the 116 has real presence unlike the 126 which looks quite mundane by comparison. As for plastic on the bodywork, never, the more chrome the better.
40 year old cars here are exempt from both tax and testing a saving of about £250 and as for numbers on the road and those on SORN (standard off road notice) to preserve the registration, there is a site which lists them all.