Looking at the pictures of yours at the top mintex, I'd say that whoever had your A1 before you has probably had the spare wheel kit fitted and then taken it out to sell separately before trading in the car or selling it on (as they are not cheap at about £200 all in) to get more cash back.
What you could do though - if on the A1 you opt for the luggage package (that comes with yet another different tray in the boot, which actually has the spare wheel screw with it to hold it in), then this fits directly above the battery so supports the base when in the upper position (if you want to lower the boot floor you have to take that and the screw on the battery tray out (the battery tray screw just slides out). The tray by itself looks exactly the same as the one I have fitted with the spare wheel, the only difference is in the cut-out underneath. The new tray I purchased had the cut out for the spare wheel underneath, the other has a cut out to fit around the battery. Separately there is the little side tray you will also need which fits to either of the 2 trays (which you can see on the left in my pictures). You'll need that as well, if you fit either of the 2 trays (above).