I am not sure this happened in any other area's of the country, but Birmingham had a VP series of numbers. For example AVP 765G. These were used on some commercial vehicles but not on private cars. They were used on some "estate cars" though.
Stocklands used to use a run of reg numbers (VOL 1, 2, 3 and 4, 22, 23, 24 JOC etc) back in the days when I worked for them. We had a few ex Flights drivers the most memorable being the one with the nickname of Mageeve who used to frighten the passengers when he walked up to the motor using a white stick, not sure how that would go down nowadaysFlights Coaches almost always had a "7" in the registration number. And if my memory is correct, including the trade plates used by Flights Garage. I worked for Flights Garage at Victoria Road, Aston and remember the comments regarding Ken Flights superstitions, such as, not having or using any vehicle were the numbers added up to "13" and him not working on Friday the 13th.