ESA (CB) A return to IR following depletion of cash inheritance

I've been awarded ESA (IR) since 2013; I've always been in the Support Group. I was on Incapacity Benefit before that. I also receive DLA (Lowest care; lower mobility)

4 years ago, I received a cash inheritance (upper 5 figures) I reported this to the DWP the same morning it was credited to my bank account; I was immediately put on ESA (CB)

Straight away, I cleared all my credit card and personal loan debt (25% of the inheritance cash)

I began driving lessons and purchased a washing machine and PC to replace old ones that had broken before (12% of the inheritance cash)

Naturally, regular payments of rent, gas, electricity, water, food, travel, etc all gradually contributed to depleting the inheritance over time.

Spring 2024: I wrote to the DWP to report the cash had fallen below £16000; then later in 2024 to inform them it was now below £6000. I requested they review my claim and revert me to ESA (IR) All financial account evidence was provided.

I didn't hear anything from the DWP for months, so I began phoning each month to chase the claim, but each response was vague and didn't enlighten me as to any progress. They did ask me to send in further bank statements to show I hadn't intentionally deprived myself of capital. I sent the requested documents in December 2024.

I got a call from a decision maker in January 2025 who apologised for the delay, but even they didn't tell me if I had been reverted to ESA (IR) either.

The ESA have done nothing further and it's now been 13 months since I first wrote to them reporting my money was below their thresholds. I am still on ESA (CB) and I continue to pay my full rent with my benefit money.

How can I be awarded Housing Benefit if I'm still on ESA (CB), even though I've had less than £16000 for over a year, and less than £6000 for over 10 months? I'm yet to be informed about when my managed migration from ESA to UC is due to happen.

My local council have recently awarded me full, backdated, Council Tax Support, but can't give me Housing Benefit unless I apply for UC.

Should I apply for UC now or do I have to wait for the managed migration by the DWP? Will I lose money in transition and/or my ESA status if I apply now?

Is there a time limit as to when the DWP can make decisions. Waiting 13 months for one, with no sign of progress, isn't right, surely...? Should I make a formal complaint?