Harrods has not always banned uniforms. As a University Cadet on ULAS, whose Town HQ is a short walk from Harrods, we used to provide a Guard of Honour for the University Chancellor (the Princess Royal) at the graduation ceremonies a couple of times a year. Parade over, we would return to the THQ to demolish a barrel of beer and then walk down the road - in No 1s - for afternoon tea at Harrods: the deal was 'all you can eat' for the fixed price (at £4.50 this dates me somewhat). There were no problems with the uniforms and Harrods's staff (and other customers) always seemed to tolerate us!
Happy days. That said, I have not bought anything from Harrods, even though I live fairly close to it, since it was bought by Mr Fayed: I don't wish him the trauma he has suffered in losing his son, but I have always thought him a rather dodgy character who does not deserve my business.