Sorry It's not Swingewood

I am Paul swingewood grandson of William Swingewood. I am currenlty developing a website that will hopefully help identify Swingewood Glass and it's history. -->
http://www.swingewoodglass.org/Your piece does appear to be Stevens & William though. Further research in the Stevens & Williams pattern books will prove it but that will be a task in itself. The books are (currently) housed at Himley House. They won't just let you thumb through them though. God knows i've asked so many times. You'll need an approximate date and start looking in the volumes of that year. I can't remember the name of the young woman who was in charge, she's now moved back to Scotland I believe. The whole archive is in a mess ready to be moved to the new glass museum opposite the black country museum if it ever gets built.
Have you looked in '20th century british glass charles hajdamach'? I had a quick look but didn't see anything. Charles is definitely your best bet. I think he still lives in the cottage in Collis Street Amblecote.