Last Saturday our Daughter took us to the Leeds Scrapstore. It's one of a network of social enterprises, who specialise in storing scrap materials for creative play.
As I discovered it is also an amazing store of modelling materials! There are hundreds of obsolete electrical components, tubes, casings, panels, lenses, domes, switches, plastic pipes and so on. You name it they have it and in bulk!
Very reasonably priced. all you do to buy stuff is become a member at the store. To check out if there is one near you just have a gander at their website here: click.
The Leeds scrapstore