The problem is that all the other houses you could have bought for 31K back then are also now worth 72K so you aren't any better off. The only people who make anything out of rising house prices are estate agents(their 1% fee goes up) the cancellor who makes his stamp duty and the banks who can charge you more interest.
As for remortage, If you want to pay the interest on 72K as opposed to 31K then thats up to you.
