Sorry, David's right, I should definitely have mentioned the AHW collection at Broadfield House.
St Helens World of Glass (
http://www.worldofglass.com/museumonline.asp) also has some items: UGB bottles and jars, collection of trade samples of United Glass tableware produced in 1935 (bowls, dishes, cup, sherry glass, plant pot and saucer, trays, vases), Ravenhead items from 70s/ 80s (mainly promotional and commemorative ware) donated following closure of Nuttall Street manufacturing plant in March 2001.
One other publication I should have mentioned is
The Ravenhead Company Story – Glassmakers since 1842, produced by the company in 1997. I've been searching for a copy for a while without success - I suspect it would have been a very small print run. But might be worth asking your Sheffield contacts if they've come across it.
I understand that the United Glass company records from 1856-1976 are held at Hertfordshire county archives (
www.hertsdirect.org/libsleisure/heritage1/HALS) - along with Broadfield House, high on my hit list of places to go when I can clear some time for archive research.
Can you say a bit more about the Nazeing glass museum? It sounds really interesting.
Do get in touch, either here or by e-mail (click on the envelope under my name) if you've got any further questions about UG/ Sherdley/ Ravenhead and I'll do my best to answer.