just made my own bath panel
top/bottom rail 3x1" 2 intermediate and 2 outer styles 4x1"[door on its side]
3 panels 2x1" 10mm wide rebate 12mm deep outer edge 9mm deep internal rebate for 12mm ply protruding out the back 3mm but chamfered
all edges with a small roundove[quarter round ]
the frames stick out 9mm with the ply 4mm further back
the panels are held in place by a lip at the top and gravity/friction/rubber seal at the bottom
this allows a realy nice looking bath pannel with lots of storage space and instant access to the plumbing