I wonder if the designs arose independently or interdependently? I'm assuming the Czech design would be the latter - but RSW had a lot of access to Scandinavian glass, and his 1967 'Angular' vase (and similarly-shaped
1960 floorvase) bear more than a passing resemblance to a 1958 Jacob Bang vase for Kastrup (see McConnell, pg.144 for example).
It does seem that the closer you look at post-1950s British design, at least in glass, the more derivative it can seem. I keep hitting this same brick wall with much of Baxter's design for Whitefriars. It's aesthetically pleasing and very well-made, but often lacks a certain spark in an international/historical context because you can
usually find similar, earlier and better designs by other people in other countries (predominantly in Scandinavia).