Easy answer to the uninvited entry is to post at your front gate and or driveway a sign that says "No Entry". This sign negates ALL implied rights of entry to your property even by police. This applies to property which you own or if you are the renter of the property. People or businesses can only enter if they have a warrant, court document, authority of an Act of Parliament, or have given you a legal notice of entry that allows them entry or you have given them the authority to enter. If you put this sign up you must write to your Energy supplier and give them/their meter readers permission to enter to read your meters otherwise they will only be able to issue "estimated" bills. After you place the sign/s you can then sue anyone who enters your property who do not hold a legal licence to do so, this includes Door to Door sales people, members of government, people seeking election, religious organisations, charity workers and so on. You do not have to prove any damages you can just sue them because they trespassed.
See High Court decision Robson v Hallett  2 QB 939, Lord Parker CJ said (at 951):
"The occupier of any dwelling-house gives implied licence to any member of the public coming on his lawful business to come through the gate, up the steps, and knock on the door of the house." This implied licence extends to the driveway of a dwelling-house. However, the licence may be withdrawn by giving notice of its withdrawal. A person who enters or remains on property after the withdrawal of the licence is a trespasser.”
You can, if you haven't placed signs, just say "Leave my house" or similar to revoke any implied right of entry and as soon as you say this they must leave or they are committing trespass and can be sued.
Also please note that if you have used the "No Entry" or "Do Not Enter" or similar sign or have asked the person/people to leave you can ask the police to remove them.