If you know which part of the country your ancestors worked in, you should begin by approaching the local record office for that area.
Dudley Local History and Archives Service holds an extensive collection of trade directories, returns, and electoral and parish registers from the Dudley Metropolitan Borough area and further afield.
If you are researching the Stourbridge, Brierley Hill and Dudley glass industries, the Museum Service may be able to provide information. It has a large library and archives. Although we are unable to carry out research on your behalf, we may be able to tell which manufacturer your ancestor worked for and give you information about their particular trade. Please look here for contact details. Enquiries should include as much information as possible, particularly any dates and addresses.
The Birmingham and Midland Society for Genealogy and Heraldry is the principal family history society for the counties of Staffordshire, Warwickshire and Worcestershire. Advice and information on genealogy can be found on their website.
To aid your research you may want to read "Glassmakers of Stourbridge and Dudley 1612 - 2002: A Biographical History of a Once Great Industry". This book by Mr Jason Ellis describes the history of each of the glassworks located across the Stourbridge and Dudley districts, tracing the ownership of each works from the 17th century to their demise. It even includes a glassworks located in Worcester. It will provide context for what can be a confusing range manufacturers and sites.
Bristol and the South West