In the 'big' W/Fs book, J. Wuidart are described as 'old established Belgian glass importers' - they appear not to have been manufacturers, and like other European importer/agents it was a common practice to have addresses in other European cities aside from their main address (which I assume was in Belgium) - Sowerby for example had showrooms/offices in Hamburg, Paris and Brussels. Competition was big stuff and sales no doubt suffered if you couldn't keep up with the foreign competition. I have no knowledge of the two Registered designs that Neil speaks of, but might look them up some time when I'm at TNA - but no doubt if you do have a peek then the Wuidart address will be shown as 26 & 28 Bartlett's Buildings, London, EC, which appears to have been their registered London address and is shown on their adverts for 'Wealdstone' material.
For how long Wuidart had been at that address I've no idea, or for how long afterwards, either - it seems from what Neil is saying that they may have been in London from 1869, and as W/Fs agents from 1932 until the 1960s.
This practice of an agent - based in the U.K. - Registering an imported design, not of their own making, was not uncommon in the first half of the C20. some of the Czechoslovakian imports acquired this status, which make for difficulties in knowing who was the actual maker of the glass, since the Registration details show only the importer/agents name. One exception to this is Schrotter's well known 'Lord' pattern designed for Inwald and imported by Clayton Mayers.
Looking at Wuidart's adverts (1931 - 34)for 'Wealdstone', they omit any reference to W/Fs, and state only 'British Hand Made Lead Crystal', and presumably if Wuidart had exported 'Wealdstone' from the U.K., then any buyers would have been equally unaware as to the maker. Did Wuidart export Wealdstone from the U.K. to other countries do we know.
E. (Edmund) Barnaby Powell appears to have been the originator of the designs for the 'Wealdstone' range c. 1930 ......... the name being taken from the location of the company's new Middlesex address for the glass house, having moved from Whitefriars (east end of City of London).
What is intriguing in all of this is that W/Fs having developed the 'Wealdstone' range c. 1930, and having signed an agreement with Elfverson's (wholesalers and importers of Swedish glass), in 1931, for its 'sole sale' (of Wealdstone glass), then suddenly Elfverson was ditched the following year, and replaced by Wuidart. Something big had obviously gone wrong. Answers please.
Don't know that we should necessarily read into the name that 'a J. Wuidart' (founder c. 1869) was still in charge in the 1960s - that was simply the Company name and company names don't need to change just because the founder is no longer.