sounds like you missed the chance to appeal. yes, there entitled to impose such a levy and will of course because their skint! it is up to you to appeal to ABP, but unfortunately you missed that boat. sorry to here this, you certainly seem to have grounds to appeal especially given everyone's current lack of funds, and that you were going to employ people!!
>check the planning file to see if the engineer had made any such statement in writing.
>write to your council any explain your circumstances, maybe work out a payment plan/ scheme..
>or reapply for planning permission on the grounds that the contribution renders the business opportunity impossible