I think, Ken, that the argument is not whether it was
made in England but whether it was made in Czechoslovakia or Germany. It is often found with an English registration mark for Jules Lang & Co. But Lang was an importer who often registered the designs he imported - I have a sugar bowl just as an example.
See
here for an earlier discussion
I think what we don't know if whether Lang commissioned designs or had exclusive rights to them, if he did then we're unlikely to know who made them