The problem with higher minima is that they cannot be enforced and are thus meaningless. Nobody but the pilot can ever know at what point he became visual.
The CAA is not stupid (well, a lot of people have left but I am talking about years ago now
) and this is no doubt why they have not legislated a higher minima for the IMCR.
Only in a multi crew cockpit / AOC scenario can different minima be "enforced" because in that case the other pilot is supposed to spill the beans on the one who busted the minima applicable to that situation.
I think that, regarding making a mistake, there is a fair number of places one can get killed at. I am sure you will hit the ground on the Shoreham 20 for example if you step down one step too early. I once plotted that approach on the O/S 1:25k map and it was only a few hundred feet above the hill.