Running Trainers!?

I would recommend going to a running shop such as Sweatshop or Up and Running so they can test your gait, especially if you're planning on starting to run more often. I got some cheap trainers from Sports Direct before and I had quite a few ankle problems. Getting properly tested has made such a difference to my running.

Yup, ditto on the recommendation to go to a specialty store to be properly fitted. We all have our favorite brands but it's because wa also all have our foot issues or certain ways of running or whatever the case may be. Make sure you let them know you're a trail runner and how often you go and if you have any typical aches/pains.

I would also make sure that you confirm that they have a good guarantee. Both of the speciality shoe stores have excellent service and if you find the shoes aren't for you, they feel it's their fault for not properly fitting you and not listening to your needs. This is pretty vital IMHO especially since most good trainers, regardless of the specialty (run, walk, cross train) are going to set you back about $100, if not more. Check to see if they promise an exchange or refund if you're not happy.