Keef
If you rely on your unapproved GPS, and get into "difficulties", you can be sure that will be the moment the GPS decides not to work
Do you have any evidence that an "unapproved" GPS is any less reliable than an approved one?
What would you call "unapproved"? The FAA has the "IFR approved" category, which basically means it must be panel mounted, has RAIM, has no way of entering a flight plan except via its own front panel (e.g. no RS232), and probably a few other functional requirements. There is,
AFAIK, no requirement regarding hardware or software quality or database accuracy (it's all from Jeppesen anyway).
I am completely certain that the build quality of handhelds is better than that of panel mount units.
In Europe, "IFR approved" means nothing. There is the "BRNAV" category, and SOME "IFR approved" units are also BRNAV (e.g. GNSx30, KLN94B). As far as I can tell "BRNAV" is authorised as sole means of navigation at FL095 and above, IFR, with some conditions probably; not really applicable to a UK PPL.
In theory, a RAIM GPS ought to warn if the signal is being jammed in a particular manner such that the satellite fix still computes, but the computed altitude is wrong.
I fly with a KLN94B/KMD550 (cost maybe £10,000) and it's a great piece of kit but I used to fly with a Skymap 2 portable which frankly was just as good for actual navigation (not as pretty and no stormscope display
). It cost £500, one could load the flight plan into it from Navbox thus eliminating a whole load of hassle and possible errors and it was accurate to a few yards including altitude, without exception. Had to use a "suction pad" aerial on the windscreen! I still think this is better than the Garmins because it straps to one's leg; perfect for renting and one only ever occassionally glances at a GPS anyway. The Skymap is now in my emergency bag.
There is no dispute about being able to fly without a GPS; indeed one should VOR/DME concurrently; the workload is trivial and the procedure eliminates practically all gross errors of either method. GPS+visual also works extremely well. If you get a total electrical failure then calling 121.5 is not an option... which takes us to carrying a £300 handheld radio (with a headset adaptor) as an arguably equally sensible precaution.......