@Chelsearob Indeed if there is a Wayleave and/or an Easement in place (legally they are quite different) than this absolutely has to be included in the deeds to the properly, and if there is such an agreement in palace but it hasn’t been included, then you have grounds to take legal action against whoever you purchased the properly from and/or their solicitors!
Now realistically, I am going to suggest that nothing legal was ever put in place, so the next time you come home to find trespassers on your property, you eject them (remember that the law absolutely allows for you to use ‘reasonable force’ to do so). The point being that you have to enforce your rights over your property or risk loosing them. Send a letter to (and keep a copy, possibly deposited with your solicitors) VM and ask by what right do they think they have to access your property? Probably you won’t get a response but after a reasonable time, build a rock garden over the chamber, erect a shed on it!