bookworm, thanks - can you please explain ? By the way, I was under the impression that I usually read the Rules of the Air "carefully"!!
It wasn't my intention to suggest that you don't FFB.
29 Without prejudice to the provisions of rule 5, in order to comply with the Instrument Flight Rules an aircraft shall not fly at a height of less than 1000 feet above the highest obstacle within a distance of 5 nautical miles of the aircraft unless:
(a) it is necessary for the aircraft to do so in order to take off or land;
(b) the aircraft is flying on a route notified for the purposes of this rule;
(c) the aircraft has been otherwise authorised by the competent authority; or
(d) the aircraft is flying at an altitude not exceeding 3000 feet above mean sea level and remains clear of cloud and in sight of the surface.
The use of exemption (c) would require an explicit authorisation from the CAA for your aircraft. It is not generically applicable to published IAPs.
Also, we still need to bear in mind Articles 63 and 64 of the ANO.
We have to bear in mind those articles every time we fly. But they do not permit you to justify a claim that an activity that is not explicitly approved or published is therefore illegal.