I just phoned the help line and they confirmed that they are indeed booked up for all of Scotland for the next two months! 4 Slots became available late in November in Aberdeen (nearly 100 miles from where I live in Edinburgh) after the call, so I could book one of those. There isn't even a test centre in Edinburgh (half a million people and probably the highest concentration of Tier 2 working immigrants in Scotland), and the entire discussion with them gave the impression of a very, very, very disorganised and poorly run setup. She could also not give me a good reason why I couldn't rather drive 40 or 50 miles south to write the test in England - it was just plain and simple bureaucracy that the test centre is decided by my postcode. Not happy at all by the fact that holiday plans are now delayed because ILR application will be delayed because this silly and frankly useless test can't be written within 7 days of applying as the V&I website leads people to believe
Oh well, at least I'll get to see lovely Aberdeen in wintertime.