You can find out who owns a property for £3 from Land Register Online
It's slightly more complicated for land (as opposed to buildings) as you can't do it directly on line. You need to send a plan of the area in question to your local Land Registry office
and ask them to do a search of the Index Map. They will then send you a list of any titles which you can then look up online for £3 each.
There's no chage for the Index Map search (providing the area contains no more than 10 titles). They prefer you to submit a 1:10000 OS site plan with your request, but these are not cheap. I've used an enlarged regular OS map with an aerial photo as backup, and didn't get any complaints.