My recommendation for spending the ?10k is to open up access between the southbound platform and FH station and the Perry Vale car park, owned by Lewisham Council. This would provide improved accessibility to the station for residents of Perry Vale and avoid the need for half the passengers to walk down a badly lit, steep flight of stairs, which is often a bit smelly due to its use as a public inconvenience.
Opening up access to the car park would enable faster exits for many people living in Perry Vale, a step free route for users with buggies, suitcases, or who have difficultly with stair. It would also encourage commuter parking in a car park rather than on local roads.
I know there are other worthy projects but this will have a significant effect on the largest number of Perry Vale residents, and ?10k could easily implement the necessary changes.
Alternatively the money could be spent sending the chair of the Forest Hill Society on fact-finding missions to other Forest Hills and Perry Vales across the globe. I am particularly keen to visit Forest Hill near Wagga Wagga in Australia, San Fransisco and New York.