Preston Manor is set in a lovely green parkland area of Brighton, within walking distance of the sea, in fact the maids that worked in the Manor would walk down for an early morning swim! I had a guided tour of the servants quarters downstairs, but it was free flow through the main area of the house upstairs so I had a good impression of the Edwardian elegance upstairs, compared to the hard work downstairs. There is an introductory video concentrating on the last owners the Stanfords and their life in the house. Special events take place in the house, and the walled garden was a picture of flowers and I lovely place for a rest if you have walked to Preston. It is a peaceful spot and well worth a visit.
Preston Church was also open when I visited and it juts into the garden of the Manor and has some wall paintings which are worth looking at. The organ was being played and there was a tree exhibition on in the Church at the time, so it was an atmospheric visit. It is a redundant church now, but regularly open.
You can get a joint admission with other attractions in Brighton if you have time to visit lots of places while you are there.