(1 hour ago)Ex-conductor wrote The 4xx series was Northumberland. Some of the existing services in the county are remnants of that system (419, 460, 472, 464, 473, 477). At the beginning of three-digit numbering, the 308 was actually 408.

8xx was allocated by Northumberland CC to the many independent operators, the only remnants of which are the 888 and 889. Until quite recently the Otterburn - Newcastle service was numbered 808. Northumberland also numbered its school day services 9xx. These services were open to the general public.

You sure on that? There's timetables available on Timetable World and as far back as 1977 it's always been the 308.

Blyth has always been the 3xx series, the town services being in the 38x/39x series hasn't it? 

(1977 Timetables - https://timetableworld.com/ttw-viewer.ph...6fc55d5b3d)
(1981 Timetables - https://timetableworld.com/ttw-viewer.ph...90dd144fa3)

The 40x series were the Cramlington / Ashington services.