Welcome!
I'm not very good at this yet so i'll have a go and an expert will hopefully check it for accuracy
Using the pink pages of the routeing guide Tunbridge Wells has routeing points
TONBRIDGE and HASTINGS GROUP (ie Hastings+St Leonards Warrior Square)
Farnham has routeing points ASH VALE, FARNBOROUGH GROUP (Farnborough Main, Farnborough North and Blackwater) and GUILDFORD
Ignoring Hastings as being likely to have a much higher fare lets consider
Tonbridge to Ash Vale, Farnborough Group and Guildford
Tonbridge to Ash Vale: LONDON, CS+WW
Tonbridge to Farnborough Group: CS
Tonbridge to Guildford: LONDON, CS
For the LONDON routeings you take the route to London and then the route from London
Tonbridge to London: LK, LK+SD+LB, LK+SL, LL, LL+SL
London to Ash Vale: WW+WX
Tonbridge to London: LK, LK+SD+LB, LK+SL, LL, LL+SL
London to Guildford: DK, PD, PD+SC, PD+SC+WX, WX+SC+PD
Working through these:
Tonbridge to Ash Vale CS+WW
Map CS allows Tonbridge to Redhill, Dorking and Guildford and Map WW takes you on to Ash Vale via Aldershot
Map CS allows Tonbridge to Redhill, Croydon and Clapham Junction and Map WW takes you on to Wimbledon, Surbiton, Woking and Ash Vale
So that's OK as long as the fare from Tonbridge to Ash Vale in NFM64 was no more than the fare from Tunbridge Wells to Farnham
Tonbridge to Farnborough Group: Map CS allows Tonbridge to Redhill, Dorking, Guildford and Farnborough
i'm not sure how this enables you to get to Farnham
Tonbridge to Guildford: Map CS allows Tonbridge to Redhill, Dorking, Guildford and then you can continue to Farnham via Aldershot
Tonbridge to London:
LB: allows Redhill, Croydon, Streatham Clapham Junction or Croydon, Crystal Palace, Tulse Hill, Herne Hill
LK allows Tonbridge Sevenoaks, Bromley South then Crystal Palace, Streatham, Clapham Junction or Beckenham Junction, Herne Hill or Peckham Rye
LL doesn't add much to LK except Peckham Rye to Clapham Junction
SD: this adds Sutton to Wimbledon which isn't very helpful in this case
SL: this adds Herne Hill, Tulse Hill, Streatham, Wimbledon
London to Ash Vale:
WW:allows Clapham Junction, Wimbledon, Surbiton, Woking, Ash Vale
WX: this adds Woking to Guildford
Therefore Tonbridge to Ash Vale (excluding London) allows:
Tonbridge, Sevenoaks, Bromley South, Crystal Palace, (Tulse Hill) Streatham (LK), Wimbledon (SL), Surbiton, Woking, Ash Vale (WW)
Tonbridge, Sevenoaks, Bromley South, Beckenham Junction, Herne Hill (LK), Tulse Hill, Wimbledon (SL), Surbiton, Woking, Ash Vale (WW)
Tonbridge, Redhill, Croydon, Streatham, Clapham Junction (LB), Wimbledon, Surbiton, Woking, Ash Vale (WW)
To name just a few possibilities
London to Guildford:
DK: Clapham Junction, Wimbledon, Epsom, Guildford
PD: Clapham Junction, Wimbledon, Surbiton, Woking, Guildford also via Cobham
SC: This adds Herne Hill, Tulse Hill, Streatham, Wimbledon
WX: Doesn't add anything to PD
Therefore Tonbridge to Guildford (excluding London) allows:
Tonbridge, Redhill, Croydon, Clapham Junction (LB), Wimbledon, Surbiton, Woking and Guildford (PD) then on to Farnham via Aldershot
Tonbridge, Sevenoaks, Bromley South, Beckenham Junction, Herne Hill (LK), Tulse Hill, Wimbledon (SL), Surbiton, Woking, Guildford (PD)
The main poiint i wasn't sure about was "can you use the London maps but avoid the London Terminals" - i decided you could!
Phew I hope that's right!