Thank you for all of your further replies. Its been very helpful. I didnt realise that quite so many stations were in two seperate counties (or very close to two seperate counties). There must be lots of passengers that use many of these stations but dont realise that they are in two different counties.
Sawbridgeworth is in only one county but is only less than a ten second walk from the border. While Knockholt is also only in one county but is again less than a ten second walk from the border. With both Sawbridgeworth and Knockholt the boundary is almost immediately after you leave the stations but the stations themselves are only in one county.
Ashurst is extremely close desite only being in one county as it is only about a three to four second walk from the border. Grange Hill (LU) and Roding Valley (LU) also appear to be extremely close (looks like the border is almost as soon as you exit these stations).
Doing some further research though it appears that Fishersgate and Roydon are actually in two different counties.
Birkbeck is indeed definitely in Greater London and is quite far away from the Kent border.
Here are the updated lists so far:
So far these stations are in two different counties:
Dean
Earlswood
Fishersgate
Ilkeston
Roydon
Strines
So far these stations are entirely in one county but are less than a 60 second walk from the border:
Ashurst
Ashwell & Morden
Blackwater
Dovey Junction
Eastham Rake
Farnborough North
Grange Hill (London Underground Station)
Kings Sutton
Knockholt
Middlewood
New Mills Newtown
North Camp
Roding Valley (London Underground Station)
Rowlands Castle
Sawbridgeworth
Shippea Hill
Stamford
Water Orton
Whitlocks End
Wythall
So whilst there are only 6 so far that are in two different counties there are 20 so far that are less than a 60 second walk away from the border. Let me know if i have missed out any.
Im sure there must be some others in two different counties so i will keep searching. It would be interesting if there is a station in three seperate counties but that does seem unlikely? I guess Dovey Junction is the closest?
That
www.streetmap.co.uk website seems to be the best site so far for finding out the county borders with 1:50000 being the clearest. Also that quiz website looks interesting. I will have to have a go on soms of those quizzes.