I can post some photos tomorrow, showing the detail.    The shower tray was fitted first, with tanking strip extending up the wall.  The panels were then fitted, with a 4mm gap at the base, I used bits of 4mm ply to space the panels up above the edge of the tray.    This 4mm gap was then filled with sealant, and when that had cured the small PVC cornice trim was bonded on with more sealant, to cover the tray to panel junction.