ok - so I fixed it ---very quickly
Pull the drawer out as far as you can
Grip the scored pads either side
Squeeze - gently
Pull
it pops out !
(might need to wriggle it a bit)
I found a business card lodged behind it - ( note to self - dont put business cards in this tray!)
Replacement
Line it up and push it back all the way until it clicks!
Easy (when you know how!)