I concur, all you are legally required to do is avoid the published ATZ. Dont forget that in the UK all ATZs at government aerodromes, (RAF,RN,USAF etc) are active H24 REGARDLESS of whether or not the aerodrome is open.
As has been said, common sense and good airmanship has to prevail, however it doesnt help that a small number of military ATC units have a very odd attitude to providing an atc service to transitting aircraft. For example, Lakenheath, (who admittedly are not a LARS provider), refuse to answer aircraft who call on VHF on a Saturday and Sunday. Yet they and Mildenhall are still launching and recovering high speed fighters and large transport aircraft 24 - 7.
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It wasn't me.