Firstly, I spoke to the police and they said they couldn't do anything because I likely couldn't prove he was snooping and couldn't prove that it wasn't against the terms and it wouldn't be worthy of their time investigating it and it was probably a civil or contractual issue. "go see a solicitor". Which I couldn't afford.
Secondly, local housing officer was contacted and I was asked to attend the local council about it and I sat there for 4 hours and was told to go home because they had run out of time. I got a letter apologising and attempts to get a second appointment were fruitless.
This was option three.
This was one of the points in my life I realised there is no magical state run safety blanket who will protect you from dickheads.
35. Landlord's Covenant for Quiet Enjoyment
The Landlord covenants with the Tenant, that, so long as the Tenant pays the rents reserved by and complies with the obligations of this lease, the Tenant shall have quiet enjoyment of the Property without any interruption by the Landlord or any person claiming under the Landlord except as otherwise permitted by this lease.
There are clauses covering emergency entry for repairs (e.g. burst water pipes, leaking gas) in short-term rental agreements but - as others have said - they require "reasonable" notice in almost all cases aside from dire emergency, and the tenant can still refuse entry.
It could still have been illegal, but it was definitely in the lease.
If they turn up unannounced this is actually harassment under UK law.
We had some rather unpleasant slum landlords between the 1950s and 1970s which caused a few laws to be introduced. Unfortunately the nature of being a landlord seems to attract certain people who find new and creative ways to be dicks. Not the majority of landlords I will say who are mostly pretty good, but enough to cause problems.
They probably have to do this repeatedly to meet the threshold for harassment.
And you basically did a disservice to all his future tenants by not reporting him to the police after being caught by you illegally accessing your home and destroying your property? By not reacting you basically silently allowed him to keep doing this. I would understand that he had some kind of power over you and you were afraid to react and report him, but you choose to confront him by being asshole to him, without doing the right thing and reporting him to whatever authority in UK is responsible for this.
Because of that, both of you are bad, though he is a bit worse.