Okay, so we rent privately right now, and the landlord works through a nationwide agency which is quite well known.
Today I took my two DC to a p&t group for the morning. DP stayed at home but came to meet me at the end. We got home, and through the front door could see the silhouette of a person moving around inside the house. Somewhat concerened, DP struggled to open the door as it appeared to be unlocked (it's a yale lock and another key lock for security), and when we got inside, it turned out to be a man servicing the boiler on its six-monthly checkup. He had been booked by the agent, and picked up the keys from their office, assuming the property was empty, and then when he got there and saw it clearly wasn't, that we were out for the day. He was mightily confused when we got home.
Now, we've lived here 2 and a half years, and have had several boiler checks in that time. They send us a letter a couple of weeks in advance, and we say 'yes that's okay'. This time, nothing. We've not had a single letter or phone call, and there have been no messages on our answer machine or missed calls on mobiles so we know they haven't contacted us. So they have, without our permission, handed out the keys to our home to someone and granted them access to the property. Fortunately for my sanity I recognised the man from a previous check, so I knew he wasn't having us on.
DP is now upstairs exceedingly stressed out (he has clinical depression and problems with anxiety), and I am about to make an exceedingly curt phone call. I know they are legally obliged to give us 24 hours notice before anyone comes round, but is there anything else I can throw at them for this? Oh, and we went to check the latest copy of the tenancy agreement they sent us, and it turned out to be for a different house. Last year we also missed a rental payment because they were too incompetant to set up a standing order. So this isn't their first fuckup.