Blue tarp. some rope to go through the grommets and pull it tight around the bottom of the wheels. CHeap and affective. but may move your mirrors. After that my next real cover will be one of those special motorcycle fold down cover/garage/thing similar to one of these but from the company that makes them in the US:
http://www.foldinggarages.co.uk/moto...inggarages.htm
They have one with a "floor" and it seals up pretty nice. A lot more spendy than a blue tarp, but a lot nicer too.
Similar to this:
http://www.autoanything.com/GenericP...ProductID=4286