Been busy today.
Stripped the paint off all the cracks leading to the window, filled them, ripped the old vent out, pulled all the rubbish old architrave out and a million tons of various mastics. Nothing fitted at all well, gaps everywhere hardly any connection between the architrave and the windows. Cleaned out filled the crevasse under the window
New architraves going on tomorrow with decent sealant. Maybe even a coat of masonry paint over the cracks if the filler is dried
Hopefully that is one corner fixed. Next job is to work along the wall sorting out cracks and loose paint etc then eventually repaint the whole end of the house.
Good stuff for filling cracks and repairing corners, a bit pricy but it goes a long way and does the job. https://www.screwfix.com/p/toupret-touprelith-f-exterior-masonry-repair-filler-1-5kg/7626h