My understanding is that the UK PPL holder can still fly VFR on top - if he / she "has sight of the ground" - and that could well be a mountain or hill, or hole in the cloud which is 100 miles away.
I think a court could well beg to differ with your interpretation.
Given the ANO says
with the surface in sight means with the flight crew being able to see sufficient surface features or surface illumination to enable the flight crew to maintain the aircraft in a desired attitude without reference to any flight instrument and
when the surface is not in sight is to be construed accordingly ....
..... it seems unlikely that
not fly out of sight of the surface would be interpreted differently.
Of course, as IO540 observes, this is largely unenforceable. Perhaps a case could be mounted if you've lost control of the aeroplane and crashed from the ensuing spiral dive ... but it's a little academic at that stage!