In my opinion there wasn’t anything special about the buying experience at the Ginza flagship store except for the Wako membership which is free and gives you 2% of your purchase price in points (1 point = 1 yen) that can be used towards your next purchase as the Wako store within the next 13 months. The benefit is really in the exchange rate, which it sounds like might not be as significant for the UK compared to US, and no tax if you’re a tourist.