(5 hours ago)F114TML wrote Broadly I believe,
1-99 Newcastle & Gateshead
100-199 Wearside
200 - 299 East Durham
300 - 399 North Tyneside
400 - 499 Washington (I think)
500 - 599 South Tyneside
600 - 699 Hexham, etc.
700 - 799 West Durham/Derwentside
800 - 899 Not sure
900 - 999 special/workers

Anyone able to add/ammend?

400s were hospital specialis and summer services, 413 was South Shields to Blackpool, 412 was Scarborough and 421 Bridlington, and 450-460 were hospital services to Stannington Hospital in Morpeth from various places .