HMV are selling both "NHL 2K8" and "NBA 2K8" for the PS3 for £16.99 (inc Del.)
You can get cashback through the usual sites (e.g. 5% from Quidco makes them just £16.14 each)
Next best price is £27.96 for NHL 2K8 (Amazon) and £29.00 for NBA 2K8 (Zavvi)
***PLEASE NOTE***: It appears the price of NBA 2K8 has gone up to £39.99. I am putting this note here, instead of altering the post to save confusion and in case it should alter again. NHL 2K8 is still available for £16.99 (see link in first post).
The No. 1 rated next-gen NBA simulation returns with redesigned Signature Style graphics, a new animation system and groundbreaking "Slam Dunk" mode. New defensive controls give you more control of your player than ever before, and an all new camera system makes you feel like you are part of a real life NBA broadcast. For the most complete and authentic NBA simulation there really is only one choice - NBA 2K8.
The top rated NHL franchise returns with an entirely NEW NHL EXPERIENCE featuring revolutionary right stick controls, all-new goaltending, a ground breaking face-off system, and stunning next-gen visuals highlighting redesigned player models and animations.
The NHL 2K franchise continues to be the most innovative in the genre - each game has been rated No. 1 for the last five years. When it comes to Ice Hockey, there really is only one choice - NHL 2K8!