Shopto.net are selling arcades for £139.99 http://www.shopto.net/page.php?page=dettagli&codart=XB2AR02&n=XBox%20360%20Arcade%20Console%20HDMI&p=XBOX%2036
Play.com have the old core consoles for £149.99 with Forza 2, Viva Pinata, Xbox Live Arcade Unplugged Vol 1 and an extra controller.
http://www.play.com/Games/Xbox360/4-/4977139/Xbox-360-Core-Console-+-Forza-Motorsport-2-+-Viva-Pinata-+-Xbox-Live-Arcade-Unplugged-Vol-1-+-Extra-Controller/Product.html?dpr=2524&P36=8984CG
I'm really tempted myself but can't get past the RRoD...
Edit: For those wanting a hard drive, Argos has the 20gb consoles for £179.48. They also have an offer on where you can buy the console, an extra wireless controller, GTA4 and Halo 3 for £228.91.
Edit 2: I'm told Sainsbury's are selling the core console + Fifa 06 for £129.97 in store.