Does anyone know if there are particular LU stations where Railcards can
be used ?

I'm pretty sure I have used a Network Card at the LU window at Tottenham
Hale to buy a return rail ticket. I got one ticket which had CSN printed
on it, maybe concession ???

The reason I ask is that when I tried to use my Network Card to buy a
Discounted All Zones Travelcard at West Finchley they told me I couldn't.

Any ideas

Tottenham Hale is served by National Rail routes so they would have to
accept railcards.

Some posters have commented in the past that you can use railcards at all
London Underground stations but that is not the experience I had with my YP
railcard.