Wow, by far the most interesting post on this forum for a long while.
You have the added protection such as it is of the
New Homes Ombudsman Service . You will need to go through the builder's complaints procedure first with, I suspect, many steps to take.
Please name the housebuilder.It is crystal clear (a slam dunk) that you have been mis-sold. It can never be argued otherwise and the housebuilder wants it kept quiet hence the disclosure agreement condition.
Question is:
Could the estate roads ever be transferred to the local authority now? Were they inspected by LA highways during construction? Do they even meet the Section 38 Agreement standards?
I suspect the builder abandoned the Section 38 Agreement because the LA would never adopt the estate roads.
So you and other early buyers, have clearly been mis-sold and should not have to pay these estate charges at all.
Obviously, these charges will increase over time, so any amount of "compensation" would not guarantee you would not be out of pocket in the long term.
You need to employ a solicitor to act for you in your interests. DO NOT use the builder's solicitor or any firm recommended of suggested by them.
You may be able to have the Title Deeds changed so that it is written in that you and subsequent owners (your house is now worth less than one with adopted estate roads due to the ongoing cost) are not required to pay the management costs.
Quite what would happen if the builder ceased trading I'm not sure - why you need a solicitor.
If, and its a big if, the estate roads could be adopted by the LA, then the more buyers that have been mis-sold make a claim the more pressure it would put on the house builder. Again your solicitor may wish to make a class action against the builder.
As a minimum I would suggest you would need ten years estate fees rising by 15% per year to ensure you are covered.
It is high time this estate management fees rip off aka "Fleecehold" was ended.
Please also write to your MP and Michael Gove.