I replaced my rear springs at the weekend two tools that made it easier/single handed were:
A lever made from a bit of channel, angle and a couple of pads to give it some angle to push down. The angle is bolted on allowing it to be used both sides.
Also a pin with the first 50mm tapered this makes aligning all the washers and spacers at either end of the spring a doddle, once all lined up use the fixing bolt to push the pin through and all the washers and spacers will be in situ.
