I had trial flights at Barton and Manchester and I'm now learning at Manchester. Would have tried Liverpool but MAN is a 10 minute drive, Liverpool much further.
I don't want to bad-mouth anyone but I wasn't impressed with Barton - won't go into it in detail but I went into the trial flight enthusiastic and came back almost totally deterred from learning to fly. However maybe I was unlucky, obviously Barton is very popular so it must have something going for it, although a couple of others I've talked to had similar experiences to mine.
My trial flight at MSF was totally different. I've always found that everyone at MSF is friendly, knowledgable, helpful and professional and my enthusiasm was restored by the trial flight there. OK it'll never be as cheap as Barton, you do occasionally get delayed, and you have to go to Sleap for circuits. But I've only once had to hold more than 5 mins waiting to take off and there have only been a couple of times when I've had to orbit for long before landing. And I enjoy going to Sleap for circuits.
My suggestion is try a trial flight at both, or at least go and check them both out.