In the (distant) past I’ve been able to buy a ticket to extend a Travelcard from the boundary of its validity to another station. Today I’ve tried to do this at the ticket office at London Waterloo (boundary zone 6 to Staines) and the member of staff said this wasn’t possible and that I’d have to get it from the last station within the zone the Travelcard is valid (Feltham). Before I query with SWR, is there anyone that can confirm whether or not extension tickets are still available for purchase please? Thank you