GPS approaches approved in the UK; and
UK Aircraft approved for GPS approaches
are two totally separate issues.
There are no GPS approaches approved in the UK.
There are plenty of UK aircraft with the required equipment and approved to make approved GPS approaches (where they are legally established - in countries other than the UK).
As for home-made approach..........since the lowest height legally allowedin IMC under IFR is 1000ft above all obstacles within 5nm of the aircraft...........there is little to be gained by using GPS over a VOR/DME some 20nm away or even some ndb/ndb crosscut.
"most likely a CAA advisory thing but not law."
Not law - but one would be reckelss to ignore the advice of the foremost UK safety authority and thereby cause accident and/or injury and/or endangerment.
Reckless operation / endangerment is clearly spely out in the law!
One of the probable reasons why the CAA are taking a cautious line with regard to GPS approaches is because one of their own was killed in a helicopter accident some years ago...........while the G reg helicopter was making a home-made GPS let-down in the UK!!!!!
Regards,
DFC