Not so, I'm afraid, Englishal - not in my copy of the ANO, anyway...
28 (1) In relation to flights within controlled airspace rules 29, 31 and 32 shall be the Instrument Flight Rules.
(2) In relation to flights outside controlled airspace rules 29 and 30 shall be the Instrument Flight Rules.
Minimum height
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 of 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.
29(a) is the authority for unapproved instrument approaches (unless you want to quibble about 'necessary'); but otherwise 28 makes it clear 29 does apply outside CAS assuming you are IMC. If you are VMC below 3000ft then you can go lower - but that wasn't the point of the original question.
Tim