I've had a sofa in storage for a while and the material needs a good clean? What are the options to clean it? Sponge and soapy water or could i use a Vax machine?
I'd use a hired carpet cleaner. If there are stains you might have to use a stain remover before using it, but all in all you'll get a better clean from something sucking up the dust and dirt.
Don't use a steam cleaner as this can shrink the material and damage it.