The relevant bit from RAF Dress Regs is
Wearing of Uniform in Public (UK) (QR 199)
0110. All RAF personnel at UK units should normally wear civilian clothes when they are not required for duty. However, unless otherwise ordered, No 1 and No 2 uniform modes may be worn routinely in public, on public transport, on foot or in private transport. This ruling must take into account security implications and a commonsense approach to local situations. The remaining paragraphs of this Chap also detail particular situations when uniform can and cannot be worn. Local orders, i.e. SSOs, SRO’s, etc, will detail current circumstances regarding the wearing of uniform. Uniform is not to be worn on the following occasions:
a. When participating in non-Service parades (e.g. on Remembrance Day, Battle of Britain Day, etc) serving officers are forbidden to wear uniform if conditions require them to appear in the ranks with serving or ex-Service personnel below commissioned rank. This does not preclude the wearing of uniform by those officiating at a saluting base or appearing officially with a party of civic officials.
b. Uniform is not to be worn by prospective or adopted parliamentary candidates at political meetings, or while canvassing, appearing in public or engaged in any other activities connected with their candidature.
c. Uniform is not to be worn at functions where fancy dress is worn; the wearing of uniform of obsolete design, which is clearly distinguishable from the pattern currently worn, is, however, permitted.
d. Uniform is not to be worn by personnel engaged in temporary or part-time civil employment or while seeking such employment.
d. When visiting Public Houses or places of entertainment and/or consuming alcohol, unless at a recognised Service function or when officially representing the Service at an external function.
f. Relaxed Dress. There may be occasions when a relaxed form of dress is appropriate, such as in DOR activities. Any Commanders proposing to initiate a relaxed dress policy is to obtain formal approval from the Chairman of the Dress Policy Committee.[
I don't know why there are 2 sub-para ds and no sub-para e.
And yes, it is sad that I know where the regs are.