FWA has run out, what to do?

[shouldbesleepingnotscrolling]

I work in a large finance company part time, I have always had a flexible working arrangement in place which is re-entered into the system every 6 months and signed off by manager and then HR.
I moved departments a year ago and before I moved I confirmed with my new manager that he was happy with the hours as my DDs nursery hours were booked around them.
After 3 months he started asking me to change days/hours.
At first reminded him of the agreed FWA and that the school runs/nursery times meant it wasn’t easy to do. He has asked a few times but now my FWA has expired and he hasnt realised.
Im too worried about resubmitting it as I think he can insist I change now. I have checked and the nursery have no availability for Mondays for the next academic year (which is when he wants cover for) and as I have a fairly long commute, Id struggle to get back for school run even with after school club for my eldest.
Is there anything I can do/any suggestions for how I can retain my current hours?

I should add I have been flexible to an extent by coming into the office more since I joined the new team.
Also my manager has not been consistent with the new days he wants me to work. First he wanted me to cover Fridays then Mondays, I feel like he doesn’t realise how hard it is to rearrange everything around my hours.

Bump😊

Possibly speak to HR rather than your manager in the first instance? If you DO resubmit a request, make sure you emphasise what you have written here, I.e. nursery have no cover on Monday and you can't get back for the school run.