The patio door is about 15 years old and fitted with two GU bogies with a connecting rod between the two. The springs which 'throw' the door to the frame when the bogie hits the 'keeper' have broken. I have phoned a couple of local installers who only seem to want to fit a complete new frame and door. I have emailed upvc-hardware.com who have a picture of the bogies on their web site, alas, they say they have none left and unlikely to be getting any. Seems stupid to spend hundreds of pounds for a new frame and door .. just for a couple of springs oreven a couple of bogies!