hmmm, interesting. seems a bit weird to me that they would make the test pressing of a UK release in california. but there might be a logical explanation for that.
test pressings are very rare. they normally only make a couple of them (five? less?), as they are only made to check if everything is ok before pressing the vinyl for real.
value: not a clue. with items this rare, it depends on how much interest there is (are there many pixies collectors out there still?) and what people want to pay for them. it's hard to predict what this would do on ebay for example. might be hard to get $50 for it, but it might as well reach $500 in no time (although this second option seems the least likely to me).