There is nothing which indicates that North Denes is "notified" (the legal term) as a licensed aerodrome/heliport. To be "notified" it needs to either be shown in the UK AIP or NOTAM. I can find no record in either.
As to the legality of conducting certain types of flights, you need to refer to the ANO Article 126. It may be interest to know that my understanding, after discussion with relevant CAA Departments, is that the aircraft commander is ultimately responsible for determining if his/her flight requires use of a licensed aerodrome, and if it does, establishing that the relevant aerodrome is licensed at the time of flight. However, the aerodrome operator (if licensed) is responsible for notifying any changes to the licensed state.
As for apparently carrying out instrument approaches to an unlicensed aerodrome, while operating public transport, without Air Traffic Control (not A/G), is this really correct? The UK normally requires ATC, or exceptionally AFIS if ATC is available from an adjacent unit (Barrow Walney Island springs to mind), have never come across using A/G. There must be something that has not been mentioned that has caused CAA to agree to such an operation.