Bit bummed after missing the £5 deal on steam the other day and after a bit of searching I found this. Not the cheapest its ever been there, but its definitely the cheapest at this point in time for a digital download at £4.78 after paypal conversion.
Includes the game and all released DLC. I'd go as far to say as the normal asking price of £15 on steam is well worth it to begin with! Some of the DLC is a bit nath. But Old World Blues is worth the extra for this pack on its own over the base game.