Can I just play devil's advocate here?
Last winter from October-March our DD's were £66/£67 less than they would have otherwise have been and we all benefitted from the EPG rates. One could argue that without these interventions our DD's would have been been mouth-wateringly high. Roll on 1 year later and utility rates have fallen considerably although the HMG interventions should not be kicking in when the EPG safety net scheme finishes in March 2024.
If you haven't already done this, I'd suggest you look at your annualised kWh consumption (not costs) from Oct 1st 2022 - October 1st 2023 (or thereabouts) and apply the tariff rates that you are currently on for the whole of that consumption, add on the standing charges and divide by 12. Is this anywhere near the DD figure Eon Next are suggesting? I'd also suggest requesting a repayment of some of your credit leaving a small buffer in case the winter is worse than it was last year.
Your situation is the reason I decided to go onto Variable DD - as there is no 'haggling' as to the level of the DD and my account is currently @ £0