I think the unusual circular mark on the base is in fact the remains of the pontil scar - seem to recall we've discussed this before. Have a feeling that Continental workers use/used a hollow pontil rod as opposed to the solid type used in the U.K. - the hollow rod leaves a larger diameter scar, but one which doesn't need grinding down afterwards.
Anyway, probably gives support to having been made outside the U.K.
At least I think that's what it is - could be way wrong

Sorry, but can't help with attribution - like the blue though. Wouldn't be one of those Dutch faux antique looking pieces I wonder - was one of them called Antiqua? One of their characteristic features was the large, irregular and flat bubbles, quite massive some of them (the bubbles I mean).
Ivo will know what they are called - although I seem to remember most were some shade of brown.
my pc about to give up the ghost and running very slow, so can't flick around the web to investigate at the moment.