If its a ex-demo car the chances are that someone has tried to close the door with the sidescreen in the wrong position and this has resulted in the frame being mis-aligned.
You could try some very gentle manipulation, and see if that makes any difference , if it does then try a bit more , but do it gently and incrementally.
You could take it back to MMC but I appreciate that is quite a long way from Skipton to Malvern and not an option to be taken lightly. You could see if a more local dealer would honour the MMC warranty?
