NR, not sure if it is in RAF QRs but in dress regs. How else would one salute on entering an office?
I have been on several units where it was mandatory for people visiting SHQ to wear headress. This is in contrast to US practice of uncovering when indoors. Indeed at the Commisary in Kef there was often a sailor instructing us to remove headress when we entered.
In UK this has crept in too, mainly to get round the need for ORs to salute Officers when they are out shopping in town. Now that would get certain shop assistants all righteous with people snapping to attention all the time.
As for travelling in public in uniform, it was one occasion when a junior officer was entitled to 1st class travel - when wearing uniform.