That website may be able to assist, but don't be fooled into thinking it is the Government site - it isn't, it's a commercial site.
Since the land you are maintaining doesn't have an 'address' , if you are in England/Wales you could this enquiry service to identify whether this piece of land is registered or not, and hence who the owner is. It costs �3.
http://www.landregisteronline.gov.uk/lro/servl et/TitleSearchServlet?searchType=map This is the official Land Registry site.
Having done that, if it is registered, you stand little chance of claiming it. If it is not registered, phone the LR for advice on making an application based on Adverse Possession or post again here for more help.