If it's only just hitting shops in the US, it'll be a few weeks before you can get it from UK retailers. My guess is that it won't be on the shelves until mid to late October.
I'd be very surprised if anywhere were selling it in the UK yet. They'd have to ship it from the US themselves rather than use the usual distribution channels.
Also - none of the online stores I usually buy from have it - but in my experience (and I have to agree with Zander here) - we usually have to wait a little longer over here in the UK for new releases anyway.
Please don't buy it from Amazon.co.uk their are other UK based RPG specialist (both mail-order and local game shops) that you could get it from for the same sort of price. Its not like Amazon.co.uk ever seem to discount much more than the postage anyway.
I recommend Orcs Nest in London http://www.orcsnest.com although they are only just announcing City of the Spider Queen. Normally gets things in about a month after the US release.
I used www.leisuregames.com and had great and quick service to Germany.. and this was during the GenConUK weekend when they were there so the fact I got my order so quick was pleasantly surprising.
I can also reccomend leisure games. I have ordered several items of them and have had nothing but excellent service from them. They even pulled an order from the delivery bag when I rang up and asked them to after finding out that I could'nt actually afford the book and pay for food.
Are you sure, leisure games sends me an email every week about the new releases they get in. And their catalogue (the online ordering one) seems upto date with what they have and haven't got in stock.