In the May 1975 timetable the following places in Yorkshire / Lincolnshire / the North East had one or more direct trains to / from London, but no longer do (to the best of my knowledge, please correct me if I am wrong)
Goole
Thorne North (yes really, at 13.46 to London, with no return working)
Lincoln St Marks
Market Rasen
Habrough
Barnetby (not on Sundays)
Grimsby Town
Cleethorpes
Stockton (a sleeper from KGX, no less)
Billingham (ditto)
Seaham (ditto)
New Pudsey
Bridlington (summer Saturdays only)
Filey (ditto)
South Elmsall (Saturdays only from London, one train only; also at 22.53 to London every weekday)
Huddersfield (one evening train only, to Halifax; and one on Saturday mornings to London from Bradford Exchange via Halifax)
Settle
Appleby
Rotherham Masborough
Middlesbrough didn't have a direct London service in 1975 - the Tees-Tyne Exec was only introduced later.
Did have a service in 1975, which was lost, then reintroduced by GC:
Bradford Interchange (assuming we regard it as the same as Bradford Exchange, which it isn't quite)
Halifax
Wakefield Kirkgate
Eaglescliffe
Hartlepool
Sunderland
Also Chinley and New Mills Central in Derbyshire on St Pancras - Manchester Piccadilly services, as mentioned on another thread.
Edited to remove "Keighley" which I had accidentally put in.