Don't waste time with a shop, they will only sell you trainers on the back of it.
Invest in having a complete analysis done. I saw Stride UK in Brighton, cost no more than a descent pair of trainers, worth every penny.
Stride UK | Specialist Running Shop | Online Gait Analysis
Video Gait Analysis in Brighton
I visited StrideUK in Brighton, they do a full body analysis of you running, they film 360 degrees, head to toe, provide you with a full training program and list of suitable trainers for training, trial and racing. I had an ITband problem, saw their details in...