Patriot Games in Sheffield's expecting them then or thenabouts (whenever the distributor gets the stock is usually how it works). They do mail order, but I don't think there's a pre-order up yet.
When Essentials releases were sent to WPN stores early in the US my experience was that all game stores (or perhaps all bricks and mortar game stores) which got their stock directly from Esdevium had the stock on the WPN release date.