Took some vertical blinds down to decorate, there were issues with the beads around the windows and got a plasterer in to sort out. He did me a favour and neatened up the plaster around the window recess but in the process covered up the holes for the blind fixing. Trying to put a plug in for a new fixing and getting refusal at 20mm. Its plasterboard initially but then a lintel presumably. Its an 80's house. The old screws are 40mm so can't quite figure out how they went in and the way forward. Any ideas please?