Dora9 & Leadsled:
Remember that, in RAF service, there were a bunch of other regulations as well as the Pilot's Notes for each type - Squadron and Station Flying Orders, Air Staff Instructions from Group and Command, and, at the top, Air Ministry Flying Orders or (later) Military Flying Regulations. The 1966 Pilot's Notes are as you say (though mine is labelled AP 101B-5510-15), but my recollection from the 60s is that among that other mass of rules there was a blanket ban on all flick manoevres in all RAF aircraft. From 1999, for a few years, I flew the Tutor (which had replaced the Bulldog, which in turn had replaced the Chipmunk in the RAF) and, most unusually, flick manoevres were (maybe still are) allowed in RAF use.
These days I fly a Chipmunk on the UK civil register, and we have a Flight Manual issued by the UK CAA. It is remarkably vague on aerobatics, and does not list manoevres, either permitted or forbidden. Flicks are not mentioned. One limitation is that aeros are prohibited unless the rear fuselage anti-spin strakes are fitted. Slightly odd, that, as my RAF experience on the type started before the strakes appeared, and we certainly did aeros without them.