Hi Paul
The multiflex board has two black knobs attached to the grey frame of the MFB
Unscrew the black knobs fully until they won’t turn anymore
There should be a gap between the black knobs and the silver frame, you should be able to see a red sticker under the black knob ( on the silver frame)
Press the black knob downwards and turn through 90 degrees to release each fixing , simply lift the MFB up and out of the van
The seats are removed by popping out the plastic caps on all four rails just behind driver / passenger seat, with a flat blade screwdriver inserted into the rubber seals just behind the rear edge of each plastic cap, near the top of the cap, push the screwdriver gently toward the cap (front of van) the plastic cap can then be popped out by raise the screwdriver whilst maintaining slight forward pressure,
Next - see the join in the aluminium rail about 30cm back from the front of each rail.
With the flat of your hand apply down word pressure on one side of the rail, in front of the join, and push forward, one side of the rail should come loose, so you can carefully remove it, repeat for all rail pieces that need to be removed to get the chair out.
Slide the chair fully forward into the opening in the rail, the chair should now be able to be lifted up and out of the van (they are heavy)
I hope this helps