For anyone looking for a Seiko PADI who gives up on waiting for Amazon, WatchO are selling them for £315. I believe you can also use code 'SEIKO5' to get a further 5% off.
http://www.watcho.co.uk/watches/seik...atch-srpa21k1/
For anyone not keen on the Amazon warranty, note that WatchO are extending their warranty to 3 years on the above.
edit p.s. I've confirmed with them that this is UK stock i.e. so 2 years Seiko UK warranty with the third year provided by them.