Hi,
The route via Edenbridge/Edenbridge Town is out as previously described.
EDIT:
I checked again and there's an odd situation where an Edenbridge to London Terminals via East Croydon season ticket *is* valid from both Edenbridge and Edenbridge Town. That flexibility doesn't appear to extend to any other station. Maybe that's what was heard being talked about?
However, an Uckfield - London Terminals ticket is valid for Uckfield - Upper Warlingham - Walk - Whyteleafe - East Croydon - London.
(Check out the National Rail website for an Uckfield to East Croydon via Whyteleafe itinerary to see it)
With this validity a season should also cover the East Croydon to Purley part, allowing an Uckfield - East Croydon - Purley routing.
Cheers,
Mr Toad