Design registration dates to March 1938 but that number's not listed either in the Glass Association Blue Book of Registration Numbers or on the Great Glass website, so it's either been overlooked or the registration wasn't filed under glass (that's not unknown!) so we can't say who made this yet. If you can get to the National Archives at Kew you can look up the number there and it will say who registered the design.
Can you get a closeup clear shot of the registration number please?