Thanks. You can get flush casement plastic now also but thought these look nice and really impressed with the fitting. Cost an arm and a leg though.Fair play for going timber. Much nicer.
Only outstanding thing is to clean off some of the old upvc /mastic stuck to the sides. Reckon this would do it?
https://www.screwfix.com/p/norton-preparation-brush-set-25-50mm-3-pieces/380jf