very small hole betweem switch button and side of handle. A flatblade jewellers screwdriver needs to be pushed down to release the catch. I've just read how to do it on this site via a different question where it mentions be careful as the small catch can snap. Well it did so now I'm having to look for a replacement switch!!!!!
The previous answer had a link to a spares website that looked OK. I'll have to track back and see if I can find it.
howtomendit.com for free repair help, information and advice.
Try fixfault.com to fix vacuum cleaners.