Myself, but with the help of SWMBO, hold this, push here, no, no, your doing it wrong, etc, etc.
Fitted 3 larger ground floor windows and 3 external doors and a conservatory before, but these will be the last 3 I do myself. One is ground floor, so easy, one is half way up stairs so more difficult and the last one is the upstairs bathroom but access can be had from a Kitchen extension roof so not too bad and the window is smaller and easy to handle. Unfortunately in the old windows, the beading comes out from the outside so its difficult taking the glass out higher up than the ground floor.
There are 3 final large upstairs windows to do, but no chance of me doing those and they will probably wait till later in the year or next.