Unless you want to know the average price of fieldmice paid at the 'Bird of Prey' auctions, the above won't help - it should say 'houseprice' not 'mouseprice'.
And that site won't help you anyway because it sources the same information using the Land Registry data (it buys the data from the LR).
The LR starting putting transaction prices onto their system during 2000 - so if it's any earlier, it is a non-starter.
You could try the auctioneer, but I think there is no obligation to give you the detailsl