[MikeIOW]

There are very few options that add significant value (£££) to a vehicle, I suspect.
& that has pretty well always been the case.
What those options should do is make that car more desirable to purchase over the one without those options.

I imagine I will be in the same boat when we decide on a change: Stormy had over £6K of options added....I doubt I will see much of that on changeover.....but the key is I chose them for *me* to enjoy (& I love them....even the daft 'clip the kids ears' folding headrest button has amused us a few times and is handy to clear that rear view!).
Even things like DSP - an expensive option - most people won't know the benefit and pleasure of having those features. To me, adaptive cruise is now on my "must have" list for any future car....but a secondhand purchaser of my car is unlikely to appreciate that enough for it to make a difference, sadly!

Once private sales are over £10-15K that is also a barrier to many on the finance, as you said above: that is where part-ex may be the best option.