Owning your own home

Doing some very basic arithmetic it would appear that overpaying the mortgage with the aim of paying it off in 15 years rather than 23 would save £30,000 in interest.
That's proper money.

I did a spreadsheet of this crap yesterday. If I took away what I've overpaid in the last ~3 years my mortgage would be 10 years longer and it'd cost me an extra £15-20k.