Thanks for getting back so quickly. That's basically what I wanted to
hear.

The builder I had fit the door, is dragging his heels about levelling
it up for me, so I can see myself eventually doing it. I just wanted
to make sure it was possible, I thought it was, but then questioned
why the builder would be messing around, and not actually doing it.

The door is at an angle that needs to be rotated, ie top hinge pulls
the door in and bottom hinge pushes the door out. The door is correct
in its measurements, ie corner to corner not out of skew, toe heeling
etc, but very noticable that it's not hanging straight with the upvc
frame, about 1cm out. Everything else with the upvc is aligned
perfectly and of the correct measurements, after checking with a
spirit-level etc.

Another question:-

Did you have any trouble getting an allen key to fit, it seems a very
odd size?