The great North/South divide is a load of political rubbish. I've worked throughout the country, worked with all sorts, even the Welsh, the Poles, and a strange gang of Scots ! The sooner we all get on the sooner we put this country right, The old saying " together we stand, divided we fall" the politicians love to keep us all divided. As the famous rebel Wolfie used to spout " come the revolution "
When the car was registered there were several options (the rules have changed a fair bit recently) however in the 1980's here in the UK there were two main options. you could keep the original registration if the kit was largely built from one "donor" car. those cars often kept the original car description i.e. Hillman Hunter. (not always) the other option was to pay a "new car" tax and register it with a new registration. later in the 80's there was a "Q" plate system introduced on top of the former one. this was for cars whose parts were largely second hand or of indeterminate origin. (or some thing like that) i have owned a Dutton that dates from 1978 with a "new" 1979 registration....and a 1984 Dutton with a 1972 registration. Registration plates in the UK tend to stay on the vehicle for life, you can pay for a personal plate to be registered to the car but it will stay on the car when sold unless you again pay for it to be removed and the car re-registered with and age related plate.....(number plates in the UK are designed to show the age of the vehicle at a glance) my 1979 car was "V" reg the letter "V" at the end was for cars registered between August 1979 and July 1980.
What series is your car? that will help give an estimate of its true age.....
The Hillman engine range were well rated in their day especially the Holbay (i am sure that was the name) tuned ones. it would have been considered a good choice as an alternative to Ford engined. i have seen a a Hillman engined car before at Stoneleigh Kitcar show, they are not common.
with reference to the starter problem, surely removing the whole engine is not such a great hassle? even if you only move it forward in the engine bay? it was the preferred method for me when replacing clutches on my Phaetons.