Your ex should be providing everything necessary while your children are in his care. Clothes, toys, food, car seats, toiletries. Maybe not a bike but everything else.
I suggest you email him to let him know that in future you expect him to have these things at his house. Then he has some notice to get things ready for the next visit.
Also, point out that costs have risen significantly in the last 5 years. The children are older and need more things, plus inflation, so you will need £250 a month from now on. (So he can negotiate it down to £200)
If he refuses, I’d contact the CMs and let them sort it out.