None in short ( in law )
depending on the bailiffs they will demand their cut
SO the council should properly refuse any behind the scenes deal
as it would mean they have to pay the bailiff themselves (and they wont)
[ unless they are in-house bailiffs - very unlikely]
sorry to give such a crappy answer
it is a debt ( what you owe the council ) and it can be traded ( = a chose in action but that doesnt matter ) and you have no control over who trades it to whom until it is paid off. The rate at which they can add overheads is strictly limited and you can be sure that they will stick to it
debt - bad
ignoring debt - really bad