Property law can be a minefield and many boundary issues end in expensive disputes, in some cases serious assault and murder! Boundaries can and may be shown on deeds but with older property boundaries may have changed over the years. If a person/body has been using land (doesn't have to be neighboring land) for 10 or more years, then they can claim 'adverse possession' and ownership of that part of the land they have been using (squatting). If the property is registered at the Land Registry questions of boundary can be resolved, however, Land Registry base their records on deeds and other documents of ownership so any mistakes or boundary changes can be replicated on the Register. When property changes hands law requires it to be registered so eventually all land will be registered. There's no legal requirement for unregistered land not changing ownership to be registered but it would be wise to do so as this makes sales and ownership transfers much easier. If the Land Register has mistakes any appeal has to be lodged at the Lands Tribunal within twelve years to get any corrections considered, note they consider the correction. Only in exceptional circumstances will the Land Tribunal accept an appeal beyond twelve years. The Register will identify ownership but also any rights, right of way, privileges, mortgages and responsibilities on that land. This could be access, the type of access (pedestrian, vehicular, animals etc) running a drain under the land or who maintains the fence for example. These are called 'Charges' and will appear on the Register of that particular property, Charges will not be shown on the Register of any land/owner who enjoys that right etc. Anyone can get copies of registration from the Land Registry for about £3.50.
Hope this helps?