I know this may be a day late for the op but this is something I have some limited professional dealing with.
There is no doubting that local authorities have seen massive funding cuts and stuff like this has really suffered. Decision, hard decisions have had to be made and agree or not stuff like this has suffered. Personally I wish my LA prioritiesed stuff like this above other stuff but can understand the reasoning and sometimes choices are stark.
Anyway...
With projects like this where basically what is needed is cutting back and the main cost would be manpower as opposed to materials I have had great success getting the naughty boys (community payback) club down. They love it as cycle routes are generally safer, traffic free, (we can't have billable scrotes getting hurt/splashed)there is no cost as the vegetation is simply cutback and thrownback. They are usually crying out for schemes and ideas, especially those proposed by locals.
There are more details here
https://www.gov.uk/community-sentences/community-payback
Local schemes are usually run by local probation services (not the police) and can be contacted directly. You might need to do a bit of digging to find out who runs your local probation. They don't always align to police or Counties.
Most local authorities have a youth offending team who do similar stuff and look for similar ideas - infact Ive just given my local YOT Three patches there agreed to fettle. Contact your local council and ask for the YOT.
Like anythingelse in CJ dont expect anything to happen overnight.
Once local authorities find you are willing to do stuff yourself and get off the self defensive dealing with another moaner they are generally quite supportive. We have several litterpicking groups to whom the council have supplied litter pickers bags and hoops. They then email someone the location of the filled bags and thr local authorities collect. Local clown councillors are good at getting stuff like this going. Maybe you could found a bushwacking group.
