Unfortunately they bought it in the early 90's for a "token" amount from my mothers friend, so the difference between what they paid for the site and the value it was when given to me is around 100k. Which seems to make a quite substantial tax bill. So they were as good as gifted the site originally too as they didn't buy it for market value. So bought for 600 pounds in 1991, transferred to me with value 100k 2006, sold by me 42k 2013. I am panicking a bit and am truly grateful for the help I have received here.