Another place to try might be health food stores and the health food aisles in the supermarket.
Unsweetened chocolate is actually fairly common for baking in the US.
It can also be found as "baking chocolate"
Some USA type food shops may sell it too
Yes I've been googling and a few places said this - that it was widely available there but not here. Frustrating! But cool, will check health stores.
AND... have just realised I need to do an amazon order for my brother's very specific taste in books... so actually I might chuck a couple of bars in there!