"If this is an "espag" then they are easily removable (2 screws under those plastic covers)"
Same applies to "Shootbolt" Bite the bullet and peel the screw cover off, if you're careful the original twinstick adhesive will work. Ultimately you may have to replace the handle but it's easier to work with off the window.
As another aside. Both Kitchen and Bathroom windows were/are normally held on "Night latch positions. Came to "open" kitchen window, wouldn't unlock but NOT the window lock, handle was lifting partially. Transpired one of the shoot bolts had corroded in guide sleeve in opening window frame One side worked but the window lock broke on the seized side, fortunately enough room to distort window and allow stuck side to unhook. With window open, relatively easy to strip frame parts down and rectify. Needed new lock (Fleebay) but other parts were cleaned, lubricated and reassembled. Total cost, about £8 (free postage) would have been £15 for same lock from local supplier and a total messing time of about an hour.
Shootbolt locking pins are the two bits that poke out of the window frame ends when locked, round Brass bars with anti-rotation flats top and bottom. Open window and then "Lock" it. NOW apply Vaseline or a waterproof grease to the ends and work the lock open and closed to make sure the guides are coated. No, brass doesn't rust but the monkey metal guides corrode.
Prevention takes a couple of minutes, alternative could cost £500 ish, the whole window frame could need replacement.
Regards Ian.
Edit. Now TRYING to free Bathroom window.
Edited By Circlip on 03/08/2021 09:15:38