Softus, its really nice of you to go to all this trouble and I appreciate it, first I should say that I really did not think you were casting aspersions on my Shower, I know that compared to a good quality product, preferably British made, it would come a poor second, but I was never the less very pleasantly surprised by the overall quality of the Chinese offering considering its price. However if I were a plumber I would hesitate about supplying one to a customer due mainly to the problems such as I'm having, and the amount of head scratching involved in fitting it.
I can see what your saying about the legs, however unlike Bath sets which tend to have a large dia foot with fixing holes, the plastic bolts which make up the legs on our tray are just bolt heads, and to make matters worse are in fact domed. Another factor, which now occurs to me, and that I ought to have mentioned earlier, is that the tray has a "skeleton back", how to explain this,,,, well first its a Quadrant Tray, but the 2 sides which sit against the walls have no back to them, the top of the tray which is perhaps 18mm thick is all that buts against the wall, the tray does not extend down onto the floor at the rear, whilst at the front the shower tray extends down to the floor, the effect is that the shower tray sits on the floor at the front but nothing supports it at the back except the legs. There is one leg located under the corner with the other 4 legs forming a cross pattern in the centre of the tray. What I have done is to fix a "skirting" around the corner to fully support the 2 open sides of the tray and which I will bed it onto using a gap filling sealant, I though this would make a good job of both supporting and fixing it in position, and I suppose that in view of all this, any additional support is probably not required,,,, except that the maker does say dollop a small amount of mortar under each leg,,,,and given that the legs are not that substantial, I really would like to get just a little additional support in the centre of the tray. Now to float off another idea, the void between the underside of the tray and the Plywood Floor is approx 2 3/4 inches (I'm not really a metric person, would that be about 7cm?) and I wonder if I might fix to the floor a couple of pieces of timber approx 2 1/2 inches thick, on top of which I could then apply a few big blobs of gap filling sealant, I would then be bedding the tray in on the two sides and across the middle with the legs just acting as the stops keeping the levels until the whole lot sets, from your experience do you think this a viable idea?, I believe that bedding trays in on Sealant is not uncommon?
Once again, many thanks for your help,