Just got all my rotten wooden windows replaced with some lovely
maintenance-free uPVC ones, and very tasteful they are too.
Next thing I know some nosey git from up the street is creating a fuss
about my 'plastic windows', mouthing off about how this is a
Conservation Area and it's not allowed. Keeps going on about
fenestration issues - I'll de-fenestrate him.

I think you have a case against your solicitor who failed to inform you that
you lived in a conservation area and what it entailed. Try uk.legal.

Christian.