I am going to relocate back to Berkshire and I recently visited Brimpton. They were very friendly and it's a nice place - no aircraft for hire, but there are two syndicates currently looking for members (both 172s I think). If you call them I am sure that they will give you the relevant phone numbers.
I used to live near Welford and at that time I was flying from White Waltham. I knew about Firs Farm because the Jockeys that lived nearby used to be flown out of there to different racecourses around the Country. However, I am not aware that there are any resident aircraft there.