have you looked at the workspaces at the rear of the market place/ hampden road ? - most are commercial premises, there is a lace making business, and office supplies business, an upholsterer, and similar......
there are quite a few buildings that are let and sub let........ may be worth a walk down there...... quite often there are to let signs up and stuff......
there is also the old computer performance offices above the bucks advertiser ( they look quite big though..)
but i suppose it depends on how much space you are looking for ?
there is also the couple of empty shops on the lower road like those just near judds, - these have commercial licences so maybe these maybe suitable......
just suggestions.... let us know how you get on !