I have a sliding door between the lounge and dining room. The door is an old double glazing door with aluminium/metal frame. I think it has come off it's wheels/track. It has become very stiff to open and close The back end appears to be being dragged along. Anyone know what the cause could be and how to fix it. Any useful advise would be much appreciated

Cheers

What you describe is a pocket door and the trlley wheels might be failing. Close the door completely and pry up the side of the door that has dropped. If the trolley wheel has just come off the track you might be able to get it back on by raising the door above the normal height and pushig/pulling it into the room. The track is alike a J hanging down and the wheel catches in the lip. If the wheel has totally failed you will need to remove the casing to get the door off completely.

Yes, I think the wheel is off track.