So how is para 7 in article 49 supposed to be interpreted?
It's supposed to be interpreted as defining "specified" in the context that the word is used. And it's used in the context of runways with notified IAPs.
And on the generation of DIY approaches, the AIP defines what radio aids are used for (enroute or aerodrome, including relvant IAPs) so can one assume that rule 40 prohibits their use for anything else?
The AIP, in which the notification is made, makes the intention perfectly clear, IMHO.
"3.7 Those procedures at aerodromes which lie within Controlled Airspace are notified for the purposes of Rule 31(3)(a)(ii) of the Rules of the Air Regulations 1996. Those procedures at aerodromes which do not lie within Controlled Airspace are notified for the purposes of Rule 40 of those Rules.
These Rules require that,
where an aerodrome is provided with one or more notified Instrument Approach Procedure, unless otherwise authorized by ATC, pilots requiring to use an Instrument Approach Procedure shall use only such notified procedures. This applies irrespective of whether the aerodrome is situated inside or outside Controlled Airspace." (my italics, again)
There is also an issue over the interpretation of "requiring to use an Instrument Approach Procedure".
While the words "Instrument Approach Procedure" are not used, I think there's a clear difference in intent between:
"Art 47(9) An aircraft [registered in the UK flying for public transport] when making a descent to an aerodrome, shall not descend from a height of 1000 feet or more above the aerodrome to a height less than 1000 feet above the aerodrome if the relevant runway visual range at the aerodrome is at the time less than the specified minimum for landing."
"Art 48(6) Without prejudice to paragraphs (4) and (5), [registered outside the UK flying for public transport], when making a descent to an aerodrome, shall not descend from a height of 1000 feet or more above the aerodrome to a height of less than 1000 feet above the aerodrome if the relevant runway visual range at the aerodrome is at the time less than the specified minimum for landing."
and
"Art 49(4) (4) Without prejudice to paragraph (2) [a non-public-transport aircraft] when making a descent at an aerodrome
to a runway in respect of which there is a notified instrument approach procedure shall not descend from a height of 1000 feet or more above the aerodrome to a height less than 1000 feet above the aerodrome if the relevant runway visual range for that runway is at the time less than the specified minimum for landing."