Has anyone recently had a basic sand outdoor arena (40x20) installed recently in the South East that can give me an indication of what one is likely to cost?
No but I do know someone who has done it near Gloucester (plus she did all the drainage work, which is crucial, herself as she’s in the building/construction industry) and it cost her £30k.
whatever you do don’t skimp on the drainage. If you don’t get that right you won’t be using the school whenever it rains.
Don't forget to factor in the costs of applying for planning which will probably include planning consultant fees and the costs of an ecological assessment/survey especially if you are in the High Weald area.