My new 24 volt charger arrived to day from e bay, cost with delivery £ 10.69. This is with a very nicely made connector that I will remove. Output voltage unloaded 25.4 which would seem about right for two 12 volt batteries in series at indoor temperature.
Other for sale on e bay nominally for stair lifts ranged from £ 199 down ! which further confirms my belief that a lot of the infirm are being ripped off.
When I have time and the energy, next to get the old batteries out and see what state they are in.