Farnborough could provide an approach service to GPS approaches at the various SE airfields, all the way down to Shoreham, and Manston could do Lydd, but under the UK system somebody will have to pay for the service, and it is inconceivable it would be cost effective.
Manston Radar is notamed unavailable most of the time nowadays so perhaps they are running out of funds for the more expensive ATC staff who are authorised to see a radar screen?
It is perfectly easy, and not illegal in a G-reg, to get the contour map out and develop your own GPS approach to any of these airfields. With a generous MDH, say 600ft, it is very easy to do. Just not "official" and because it cannot be inserted into one's GPS database, one needs to be pretty careful how one uses the waypoints.