The best advice is to spend an afternoon visiting all of the establishments, they are all friendly people, and decide for yourself. Ask some questions, e.g. How long has the school been operating? Have a look at the aircraft, how old are they? What kit do they have? What of the building/facilities/car parking etc? Does the club/school have a social side?
My vote would be for the Coventry Flying School (
www.covaero.com), part of the Coventry Aeroplane Club which has been member owned/operated since 1936. They currently operate a brand new fleet of PA28s. But visit them all and decide for yourself.
Coventry is a great place to learn. You have the benefit of ATC and in mixing with the 737s and other commercial traffic. Beware that this can lead to delays while you wait for an IFR movement, but nothing too serious.