Congratulations to Berwick on being awarded a 'Portas Pilot' UK Government grant to revive your High Street in the walled town: see link.(courtesy of Civic Voice). All walled towns could benefit from the advice on improving town centre shopping, This link is to that general advice "100 Ways to Help the High Street".
Berwick's bid is described by the town itself on their website. Perhaps Berwick might like to enhance its prospects further by linking its Wednesday and Saturday markets with those from other UK and European walled towns: Stirling (town description coming soon) and York are both linked by direct rail services (well Stirling is once a day and York regularly). Via London King's Cross/St Pancras, it is easy (as seat 61 always says) to change onto Eurostar for travel to and from the continental walled towns.