You can find out who owns a property via here but there is a fee for it, only �3.00 though.
http://www.landregisteronline.gov.uk/
More recently the last sale price has been placed on the register although if it was sold a while ago it might not be.
Also check the title in case any other land formed part of the purchase price such as adjoining land or whether part of the land has been sold off since which may affect the figures.
You could also try to find the sale price here..
http://www.ourproperty.co.uk/
http://www.nethouseprices.com/