Whereabouts in Warks are you Sam-B? I don't have black & white dogs and take my guys down to Herts to someone who does agility specifically for non-B&Ws! However, we sampled a few places locally first.
Although West Mids and not Warks, Nuneaton was probably the best of the bunch. Trained in an indoor school and used positive reinforcement/clicker for contacts.....were however a tad too serious for us gundog types doing it for a lark!
If you're further south Kay Laurence does good basic agility courses at Mickleton; although she has b&ws don't think they do it that seriously there but could be a good intro.
Nuneaton is ten mins away from me and we did her training there last year but it's different people doing the agility side so wasn't sure whether they would be as good