Stevenage - Roaring Meg
Debenhams, Roaring Meg Retail Park
Great North Road
Easily found just off junction 7 of the A1(M). It's less than a mile from the town centre and train station - and also from Stevenage Leisure park where things like a Hollywood Bowl and Cineworld are.
There is an abundance of free parking right outside, on the retail park, for up to 3 hours.