I bought one of these in-stre at the Stevenage store. Lots on the shelves. Reduced from £59.99 to £49.99. Multi-coloured (switchable) blade (red / blue / green) and multiple parts to biuld up to 1000 combinations apparently. All the right noises (activated , swish, clash, deactivate etc). The kit comes with Vader's lightsaber already constructed so add 3xAAA batteries and you're ready to play.
May the force be with you (as far as finding this deal goes).