There is no
official context I am aware of, in the UK, where vertical guidance is obtained from a GPS, for the purpose of flight or a landing.
Now, if I was flying some NDB approach somewhere, the altimeter was telling me I am at 2000ft and the Garmin 496 (with EGNOS) was telling me I am at 1520ft, the KLN94 was telling me I am at 1525ft, and my bluetooth GPS (which has the SIRF2 chipset with its +200ft c0ckup) was telling me I am at 1733ft, I know where I would go. And it wouldn't be that NDB approach
It would be an ILS.