A small update:
It was time for an upgrade after spending a year on and off cleaning contacts and still having the number plate lights blink sometime. Using the original housings the standard bulbs have been switched for LED blocks from CBS. These are the same as the type used for the interior lighting. Not tried them in the dark yet as it’s a really nice day today!
Did a bit of surface rust clean up on the bottom of the chassis too, mainly on the drivers side. MOT in a couple of weeks!