Colin Wilson wrote:
I need to replace a wooden 'Georgian' style window that is rotten.

ISTR there being a requirement to involve the local council / planning
regs (?) if you`re fitting plastic windows yourself - if a company is
doing it they have a different licensing system to allow them to just
go ahead...

Perhaps someone else has more info ?!?

Cant see it meself? a window frame supports no load bearing on the structure
so therefore can be done without involving council. Blimey! people take
window frames out to get the furniture in and out of the house some times
cant have the hassle of going to the council and say..."we need our window
frame out can you set up the planning regs".
So long as it properly fixed in place then alls well.