You have to use Corally Wheels, what ever tyres you can get on these wheels is obviously up to you.
As for springs, no you don't really use the springs to set ride height, it is a bit of suck it and see. We tend to measure from the bottom of the chassis to the top of the adjustment nut. This does depend on which pivot balls you have as to what the measurement will be. Personally i run the short balls at the front (As Euros kit std) and use in the region of 21-21.5mm betwen chassis and nut.