The Dame Laura Knight decanter is on page 167 of 20th century British Glass, Hajdamach.
Next to it is another decanter with enamelling.
Hajdamach caption says 'Plate 350 ... On her drawing for the clown decanter Knight has added the comment 'Decanter could be done etched in colours or in cuts rounds & ovals dull, drum dull, rest all polished'.'
So that description could fit the decoration on your vase. But... no pontil mark, cut rim?
And on page 165 Hajdamach comments that Dame Laura Knight '...was the only one of the group (he talks about a group of named designers) to combine acid-etching and enamelling for her designs for the circus range and for the 'Modern Bacchanal', ....'
That quote is taken out of context by me as too long to type it all up. Therefore it could be interpreted, as I read it, that it applies only to those designs by Dame Laura Knight, but also it could be read as applying to her being the only one to incorporate enameling and acid-etching in her work.
Difficult but I'm still veering towards it being Czech however there's nothing in the Das Bohmische Glas Band IV that's cut and enamelled that I could see. That's not conclusive of course though.
Page 122 plate 239 Hajdamach as above, there are some interesting etched coloured dots on Stuart items. No match to shape and still we have the no pontil mark but they look quite similar perhaps?