I have trouble finding trainers to fit, and haven't got unlimited funds, but I found a pair of these sportsdirect.com/avia?dsear... (the pink toning ones). They actually have a very nice cushioning feel on the heel of the foot, and are only £10, and suprise suprise, come in half sizes.
I've just done week 2 run 3, and was pleasantly surprised at how comfortable my feet were! Just a little product recommendation.