I sympathise with your problem.
I have just purchased an excellent pair of Asics trainers, partly based upon their 'running shoe advisor' locator.
All decent sport shoe shops should have the facility to film you running (free of charge) and they will be able to recommend the best pair of shoes based upon how you actually run.
Follow these two links:
www.asics.co.uk, and select the 'running shoe advisor', also, Saucony give details of some roadshows where experts can advise : www.saucony.co.uk, and select 'shoe lab'.
I hope this advice is helpful (and the hyperlinks work!)