The belt is probably broken, £8 from a spares shop - not too hard to fix. To take back off (loads of bolts),you need to remove circlip from drum axle, slide new belt one over drum and belt tensioner (little Black wheel)- it's a really tight fit you will need to lever the pully away. and re-assemble
howtomendit.com for free repair help, information and advice.
Try fixfault.com to fix tumble dryers.