I suspect the clamp and bolt in the back of your MK2 is the same as the one in the MK1 and 3. In which case, to fit a standard wheel, you need to have the alloy wheel face down, then the retaining cup inverted so that it fits into the centre hole.
The bolt should be long enough as I believe it was designed for both a full size and a space saver. But just for info, if you want to get a longer bolt, I actually bought one with a plastic thumb-turn which is easier to use. It's an M8 bolt btw.