Well, in your own way, you've seemingly found the answer to your prayer.
The way it works is as follows:
Councils know developers may well default on doing stuff like this so they force developers to sign a 'Section 106 agreement' which requires them to pay money in the form of a bond as a condition to getting planning consent for the development.
Developers do the development and complete the roads to a standard acceptable to the council. Council refunds the bond.
If developer fails to do it or goes bust, Council completes the works. The only hassle you may yet have is if the financial bond the Council took is not big enough to fund the works. I'll bet it is not - otherwise it is in the developers interests to just do it, if he is still in business.
You've effectively paid for this, of course. It was in the margin that the developer made from gaining planning consent in the first place.