Hi hbo,
I think it is probably coincidence, but there is a logic behind it in that both cars would have been registered by the same local DVLA office, in this case Manchester (NB is a Manchester local identifier, in fact if I remember rightly NA through to at least NF are Manchester tags).
The old Pre 2001 system worked by using the last 2 letters of the 3 grouped letters as the County/City/Town that issued the registration. The first letter of the group is random.
As yours is 'TCP', the T is the random letter and the 'CP' is I think Halifax.
My 126 Has 'MBE', the M is random the 'BE' is Lincolnshire, it was supplied by Burtons Fiat, Grimsby as new, so has been a resident in it's 'Home' county for all of its life. My Panda is 'EAG' E is random, AG is Hull, it was sold and registered by AB Fiat in Hull, and I rescued it in Hull, and so on.....
There used to be a good website listing all the local offices and their 2 letter identifiers, but I can't seem to find it any more.
I do know the 'S' series (SA through to SY) have always been Scottish issues though.
Hope it sheds some light,
Vin