However, the ONLY 'instruments' you need in the UK for IFR in Class 'G' are an altimeter (for telling if you're 1,000' above an obstruction) and a compass (to tell what course you're on with reference to said obstruction)
TheOddOne, sorry but that's plain wrong!
Firstly, you haven't correctly covered the equipment mandated by Schedule 4 of the ANO for non-public-transport flight OCAS.
Perhaps less well known, you also haven't considered the equipment mandated for IFR flight by the 'Kinds of Operations Equipment List' set out in the Limitations Section of the aeroplane's POH.
Not that this anything to do with the original poster's query!