my example of the deeper purple vase - shown in the link I attached - is marked with the Union flag, so there's no doubt as to its origin, and according to Hajdamach pieces like these date to the 1930's. The decoration aside, this 'conical' shape does appear to have been a popular shape during the art deco period - roughly early 1920's to the late 1940's - whereas Art Nouveau - c. 1880 to the end of the 14/18 war - is usually more sinuous in shape, and mostly lacks angular design.
The extent of T/Webb's design/colour range seems colossal in comparison with those from Richardson, although this dip-moulded/lensed effect does appear to have been common to both factories, as shown in this marked example from T/Webb (yet another conical shape), which also happens to fluoresce.
Did Richardson produce any glass which included uranium?