Xordon, if I read it right what would happen is that a payment would be made on eg 1st July for July then the next on 31st August for aug then 31 sept etc. That when on very tight budget is very hard.

I would refuse and go straight back to court as soon as a payment was missed.

Hi Xordon
I have to differ, we are looking at a period 8 weeks here.
If a payment was due on the 1st of the month and then the next due was not paid until the end of the next month, it incurs 8 weeks.
Taking into account that standing orders and direct debits go out on a monthly basis this would place an account in jeopardy (if you do not have adequate cash flow).
It is a game of catch up, and could lead to overdraft charges. If either party wish to vary this agreement then it has to be formally agreed by both parties.
Unless of course there is more than sufficient funds in the account in the first place, then it might not be a problem, but this is probably not the case.
zara

Ok so it is a dual change from 1st to last and from advance to arrears.
Idealy pay 1st July then end July for Aug.

That is a simple answer, assuming that the ex will be willing and able to pay twice in one month.
zara