The BioShock Infinite Season Pass includes both episodes of Burial At Sea. The first of which is mediocre, but the second is excellent. So an average of "decent" isn't too shabby for under £4! Thanks again, jaystan.
"I finished the episode with most of the hidden items under my belt in just over four hours, which in addition to the three hours of Episode 1, feels like a fair return for the season pass’ asking price," Brendan explained in his Bioshock Infinite: Burial at Sea Episode 2 Review. "The gameplay and AI feels stripped down, but this is all about tying up the loose ends. As we’ve come to expect with every Bioshock game, the final revelations are nothing short of breathtaking and every shot from last few minutes is framed so beautifully that you’ll want it on your wall. Irrational Games, you will be missed."