I called Valley Refrigeration and Shopfitting, the only company that I know goes back even further than C-Store, and a man there suggested I consult C.I.C Screens (cicscreens.co.uk) in Isleworth, Middlesex. The company deals a lot with bakery clients who want to shield their prep area from view but still keep an eye on the front of shop. And very fine the screens look, too. They are not cheap plastic but made of aluminium chain which lets fresh air in but keeps pests out and allow you to see through to the rest of the store. They come in all sorts of designs.
By the way, this new slot will only run if I continue to find useful websites, so I need your input. I don’t get much time for surfing, my spare time being taken up with writing best-sellers, hot dates and tap dancing (well, the last bit is true). So I throw this open to everyone.