Enforcing consent order RPI annual increase (Global Maintenance Payments)

My divorce was finalised in May 2019.
To put it mildly, it was not a nice divorce in any way and I've done all I can to keep things peaceful since then. However my ex is extremely difficult (without going into details, he's the worst kind of narcissist there is).
We had a solicitors and a formal Consent Order agreed and signed. He agreed to 5 years of Global Maintenance Payments (which was to secure the child maintenance payments, I only get £0.05 spousal as I wasn't after that), after which normal 'child maintenance' would resume. And he's made it clear that this will be reduced once it does in May 2024!
The Global Maintenance Payments are supposed to have increased annually in line with Retail Price Index. He refused to do this of course. He refuses to contribute to anything above this and he has no idea of the cost of 2 children. I literally pay for everything. With inflation being so high, if he does not increase the payments (which I know he won't) for the final year, he will effectively 'owe' me £3,000 in arrears. He already will owe me £1,232 by May 2023.
Things are so contentious between us I've nothing to lose by applying to court to enforce this increase and hopefully get the money he has owed me the past 4 years too by not increasing it.
Is court likely to agree to this?
Or will they not agree because I've left it so long? Will they thikn I'm being 'greedy' because he is paying the original payment amount still, just not applying the annual RPI increase.

I spent so much on my divorce and simply can't afford any more legal costs so I will need to do this myself.
I have googled and I believe I need to fill in a form D11 for this.
He is in Breach of Contract by not adhering to the annual RPI increase so I need to apply to court to enforce this?
I would never bother doing this if I didn't need the money.
Has anyone done this?
Can anyone help guide me through filling in the D11. Do I use the divorce case number and send to the same court?
Any advice would be most welcome.
Thank you

If it is a simple enforcement then a D11 with the original order and evidence that he has not complied should be sufficient.
It needn't cost more than the application fee which you could claim as costs.
You would need to have evidence of the RPI and increases he should have made. I think it is reasonable enough to explain the divorce etc was very acrimonious and you have asked nicely but have now been compelled to apply to court because he isn't playing ball. I guess it was less of an issue when RPI wasn't going up at the rate it is now.
I am pretty sure you use the same case number as that's the order you are seeking to enforce.
My only concern would be if his circumstances have changed significantly and he would have reason to ask for a variation of the original order. I think he'd have to make his own application for that

Good luck. Let us know how you get on.

Hadenoughnow

Thank you very much for your helpful reply. This is what I've done. Let's see what happens.