Flying suit is not an official uniform - it is a "coverall" and therefore only to be worn at work. Wearing of official "uniform" is now OK out and about due to the lack of IRA etc. However the consumption of alcohol in public by persons in uniform is discouraged.
On a different tack, note that the Boss of Harrods has decreed that military personnel in military uniform are not to be admitted to his shop because it may panic his customers. (A thread from last year I seem to recall). Personally I would deport the damned grocer at the first oportunity.
