Image shows my old distressed drive belt with some strands wrapped around the motor pulley, jamming the mechanism. Remove any damaged belt eg by cutting and clean off any debris from pulleys.

Fit new belt, by turning the large wheel by hand to slip the belt over the large wheel.

New belts for the Morphy-Richards models 48280/48281 can be found on ebay for about £13. There are cheaper £4 universal belts, but I don't know if they fit. (I took a belt from an older machine). Belt size about 535mm circumference, 8mm width about 214teeth