With respect, your mum's advice has been to capitulate to him every single time.
Do NOT let him in. You gave your notice to them ALL.
Not a living soul can enter there without your permission. Get the locks changed. Tomorrow!
Trust me, you have nothing to lose in this, he literally doesn't have the time to do anything. He can't do anything without a court order, and tbh, I don't think he'd get one even if he could get a court date inside 2-3 months.
Trust me!
I had THE
Landlady from hell, cab, shelter and some kickarse property management friends sorted me right out.
I changed the locks, didn't give a key. Told her solicitor that I wouldn't give her a key. Told her I was going to bar all viewings, all access and I called the police when she jumped the fence to try to get in.
All this during an abusive relationship. He was useless, and left me to it, and was in the house undermining me the whole time.
Found a new house, gave notice and moved, and all he did was move a few boxes on the day and pay the money.
You can do this love!
He ain't got nothing! You got mumsnet!