Got it done today but just need a few odd ends sorting out tomorrow then I can lay track down tomorrow or Wednesday.
First two pics show the new MDF sheets in place with the hinged section in place.
These next two show the hinged section in two pieces rather than one long one as before.
This one shows where the upper level section has been cut so it's in two sections.
And this one is where I had to put a support piece to support the hinged section in the middle but it will be made removable so I can still get about the loft.
But once I did all that I lifted one section up and it was a lot lighter but then I ran into another problem which is when I lift the sections up to get to the track below I only have about 8 inches clearance between the baseboard and the upper section when lifted up,because the hinged section hits the rafters above so I will have to remove the hinged sections to lift the upper level up to give me the room I need to clean the tracks below and to fix any loco and it only takes me 2 mins to undo the screws to remove the hinged sections so not a big problem.