Finally got there. Arguably a unique emporium, situated in a disused bank adjacent to a sex shop and within spitting (literally perhaps) distance of Sheff's oldest and best known shop Keep on Running.
Accelerate's place is good, with massive shoe range and keen and knowledgable staff, bought a new pair of shorts and a Mountain Hardwear top, both of which have proved worth spending the money I didn't intend to spend.