The t-shirts are tempting, but my cheapo self doesn't want to splurge £30 on one. (Saying that, I did spend the same amount on a Tears For Fears t-shirt when I saw them live a couple weeks ago...)The Hatsune Miku Bandstores page (that sold/sells the Miku Expo Europe merch) has listed some new T-shirts up for preorder:
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hatsunemiku.bandstores.co.uk
(Figured this'd be interesting for us European fans, and those in the UK especially).