Path users have a common law right to clear any obstruction to the extent of being able to pass the obstruction, but this doesn’t extend to carrying out large-scale or specific clearance works (and definitely no power tools!). Remember BW’s have different widths (and heights) that have to remain open compared to FP’s.
Most councils will be ok with a people spending a few hours with trimmers / sythes / a spade / etc if you use common sense and take care of other path users. This time of year I find if they’re cleared in May vegetation grows quicker in July so ideally they should be cleared in April.
I can’t keep a tab on every path in my county, and unless I hear different I have to assume they’re open and easy to use. People think the council knows when a path is overgrown and / or assume someone has already reported it!
If too big a job to do yourself ring the RoW department to report it as a high priority and ask for an ETA, and remember to complain if it’s not done in time 🙂 Even better would be to ask that it be put on the strimming schedule to be cleared as often as possible