Can my landlord increase my damage deposit when he increases my rent?

My landlord notified me that my rent would be increasing by £25 a month in May prior to my tenancy agreement renewing July 1st.

He’s now (14th Sept) telling me that he needs the £25 for advance rent (I paid the original amount when I moved in over a year ago) – which makes sense to me – and £12.50 towards damage deposit due to the rent increase.

He also stated that it was an “overdue payment” despite never mentioning it before. I double-checked his previous emails on this. I rent privately if that‘a relevant.

I’ve also got a dodgy lock at the moment to my flat and it takes numerous attempts to unlock from inside. I have no problems entering the flat and it unlocks from that side immediately. I’ve told him over email and phone call that it is a security and safety issue and he keeps saying he’ll get a locksmith to contact me, but that hasn’t gone anywhere. I first mentioned the issue in July earlier this year as it was always a minor issue (1-2 attempts to unlock from inside) but around then got a lot worse (6-10 attempts).

It just annoys me that he’s randomly chosen now to ask for more money when I’ve got an ongoing issue and with all the energy bills etc. increasing I’ve already been more limited financially.

I know it isn’t much of an increase really, but I also want to know if he’ll randomly decide there’s a justifiable reason to increase it again. He doesn’t have a reason to believe I won’t respect his flat as I’ve rented previously from him and always left his flats cleaner and better than when I moved it. Obviously I’ll pay if he is entitled to ask, but I wanted to check he wasn’t being dodgy there.