Fellow Amazon UK pre-orderer here. No sign of Excalibur yet and they have shifted the date again to Jan 19th. Let's see. Uncanny X-men 1 finally came into stock just before Christmas after months of waiting.
I think Amazon UK use the UK book distributor (
Turnaround) to obtain their stock and they have never had it in either. It's listed as reprinting there which is slightly worrying.
You can't order from Turnaround directly but the largest UK book wholesaler - Gardners - does run a retail operation at
hive.co.uk with some fairly hefty discounts. It's worth keeping an eye out to see if it comes into stock there. I've spotted some titles in stock there for weeks before Amazon finally ships my pre-orders.