think you're right about the lack of probability of getting an id Chris. You're right about these things being at their most prolific, probably, in the 1930's, and from what you're saying there appears to be evidence to suggest this one is period.
Enamelled floral decoration was popular with Stuart in the U.K., although this may well not be theirs - and much was produced in Czechoslovakia before 1940, and elsewhere on the Continent I'm sure, a lot being very utilitarian in manufacture.
I could be wrong, but think this is a non-starter regret to say, and as Christine says 'jugs are a minefield' (at least this sort are

)