Trev,
You could try this:
Gently prise the black plastic hinge cover caps off the top and bottom of each hinge, it may need a flat bladed screwdriver to help, tap gently upwards, or downwards on the bottom covers.
Use a kettle of boiling water and pour over the top hinge to start with with, as someone else moves the door, the hot water will cause the aluminium to expand faster than the steel pin, which will allow the hinge to start freeing from the rust.
Do the same on all the other hinges.
Follow the hot water treatment with WD40 to clear out the rust, moving the door all the time, and finish with 3in1 oil.
Replace the caps.
If that does not work, then it is a case of taking the hinges off and stripping them on the bench to clean them.