Thanks all, some food for thought there. Yes it's reasonably weighty, not thin and wimpy but not overly chunky, it feels as heavy I would expect a vase that size to feel (IYKWIM!)
I agree that the quality isn't as good as Dartington, my suspicion is a mass-produced far east version as John suggests, the bubbles are a bit squiffy and the prunt (thank you Sue, that's the word I couldn't think of last night, hence I used boss!) is a bit squiffy too and the top isn't quite level and even.