I took as a guide Ivan's design, thanks, since I have a similar recess. I built shelves on the principle of the torsion box and supported each shelf from the side walls on 4 25mm eccentric stainless steel pins 24mm long. The eccentric pins allow the shelves to be levelled with the advantage of the shelves having no contact with the walls except via line contact with the pins. The shelves have a 3mm gap each side and a 75mm gap at the back to run cables. The shelves were tested by my mother sitting on the lowest one!

Regards

Under review