There's an excellent film called "The First of the 13" about the
Dartford resignalling (made by someone who worked on it) on the
'Terminus' DVD:
http://www.amazon.co.uk/Terminus/dp/B00081MX60
Didn't mention what the other 12 were to be..but here's a guess:
Waterloo
London Bridge
Victoria
Feltham
Woking
Ashford
Three Bridges
Portsmouth
Eastleigh
+ 3 others.