The Xbox 360 premium is selling for £169.99 at Play.com while the Wii is £179.99.
Edge online reports that it's a Play.com promotion, not a change in Microsoft pricing. However at Amazon, the Wii and 360 premium are the same price.
http://www.play.com/Games/Xbox360/4-/659411/Xbox-360-Premium-Console/Product.html
http://www.play.com/Games/Wii/4-/1032617/Nintendo-Wii-Console-including-Wii-Sports/Product.html