Last night we connected up the shower waste with a length of pipe so that we could fit the whole tray in place and eventually connect it up. The wood supports have been treated with end grain protector, and the wood is pressure treated exterior grade.
With a bit of wiggling and some difficulty we got the tray in place. It is very heavy so not easy to manoeuvre but we got there eventually. The sump box fits nicely next to it and so the next task is to attach all the pipes and the Gulper pump. Then we can begin making the shower cubicle!