The house I referred to in the OP is a 4 bed detached (I'd guess by the size) and so is mine. They are a 2 minute walk apart, but around £100K (market value) difference in price. LocationX3 and all that. My mortgage is less than £100K, so I could move a street or 2 away, be mortgage-free and still living in the same sort of house. I could probably then afford that high end BMW, BUT...
in a few years that BMW will be worth not a lot, whereas the difference between the 2 houses might be £150K. I couldn't save that sort of money (£50K) in that amount of time, so I'd rather have the house than the car. As you say, the increase is immaterial if you don't cash in on that increased value, but it's nice to know you have something to fall back on if it was needed.