Japan
Probably one of the largest expanses of gadget heaven on planet Earth. Think of anything electronic and you'll find it here. The current sterling/yen exchange rate also means that you'll pay around 15-20% less here (maybe a bit more if you bring your passport with you to get a further 5% off as a tax-free purchase).
On the Yamanote line (and others) two stops north of JR Tokyo station. For a preview of one of the biggest stores go to www.yodobashi.com (Japanese language only unfortunately).
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