Go here:
http://www.landregistry.gov.uk/wps/portal/Prop erty_Search
Enter the house number (or name) and the post code, then click 'Search'.
If you're taken to a page, headed 'Buy documents', giving the full address of the house, you need to do nothing at all. That page only appears when the property is on the (electronic) Land Register. Land Registry entries take precedence over printed deeds. (i.e. the deeds are effectively redundant. You can sell the house without them).
If you find that the property is recognised by that website you can, if you want, download the Title Register and Title Plan for just �3 each. If you require an 'official' (= 'guaranteed') copy you should follow the instructions on the right of that page.
If that website does not recognise the property (i.e. it's not on the Land Register) you'll have to apply for its registration. You'll need form FR1:
http://www1.landregistry.gov.uk/assets/library /documents/FR1.pdf
and form ID1:
http://www1.landregistry.gov.uk/assets/library /documents/ID1.pdf
(You'll probably also need the services of a solicitor, but you might as well get as much of the form-filling done as possible, before you start paying for his/her time!).
Chris