Classroom robots are fun but you need lots of components or kits to make them. Lego Dacta Robotic Systems (set no 9725) is a kit which contains equipment and teacher's notes for making devices using the Robolab program.
This uses sensors and you make devices that can avoid objects, just like the robots in the story.
There are lots of robot kits available from Commotion (www.commotiongroup.co.uk) including Robo Soccer UK and Robocup Junior UK.
This is linked to a competition network, www.robofesta-europe.orgbritain.
The Lego kits can be used at KS3-4, will develop problem-solving skills and because the resources are open-ended, differentiation is by outcome.
More traditional demonstrations can be used to illustrate air pressure and vacuum. These include work with pressure pumps, Magdeburg hemispheres and syringes and are linked to the KS3 science schemes of work.