What sort of shower tray for 760 recess?

I've got a 760mm shower recess in the ensuite which I've stripped out.
I've got a pivot door and a show tray, but I think I may have bought the wrong sort of tray.
I've bought a 50mm slimline acrylic tray that I'd assumed would go straight on the floorboards with the plumbing underneath.
However, I think I should have bought a stone resin one.
I also think it would be better to have a raised tray so that the plumbing can be accessed if any leaks occur.

The plumber has advised buying a stone tray on metal legs.
Can you buy these conbined with a panel to go on the front at the bottom?
Can you get these sort of trays at B&Q or do I need to go to a plumbers merchants? The DIY stores seem to mostly sell stand-alone shower enclosures.

Buying a tray from a diy store often increase's the risk of movement on such a standard size, Get an easy plumb resin wth legs from a plumbers merchants. If u want the best advice go to where experts go,or we would all shop in the sheds,