I now have a Fleet-London Terminals season ticket, valid "any
permitted".

I assume it's valid on the mainline from Fleet to Waterloo, plus
Waterloo to London Bridge overground and Clapham Jcn to Victoria.

It's difficult to see what other routes might be permitted - via
Cobham to Guildford is a possibility I suppose, or on the Clapham Jcn
- Willesden Line (can I go to Kenny O on it?) Can anyone confirm if
there are any routes it might be valid on that I'm currently unaware
of?

Cheers,

Phil