Play are selling both "NBA 2K8" & "NHL 2K8" for the Xbox 360, Sony PS3 & Sony PS2 for £14.99 each (inc Del).
You can get cashback through the usual places (e.g. 4% Quidco, making them just £14.24 each)
The next best prices are:
Xbox 360: £29.98 for NBA 2K8 (Zavvi) and £24.95 for NHL 2K8 (BlahDVD)
PS3: £29.00 for NBA 2K8 (Zavvi) and £27.96 for NHL 2K8 (Amazon)
PS2: £15.49 for NBA 2K8 (PowerPlayDirect) and £15.49 for NHL 2K8 (PowerPlayDirect)