This month's Which puts the 180 gbp Ryobi CD1-1803 as best buy. Second, Bosch PSB 24 VE-2 at 99 quid Third, Makita 8443D at 335. Fourth, Hitachi DS14DMR at 265
Both the Makita and Hitachi include a second battery, though.
Unusually, they gave a 'don't buy' to two models - the B&D CD18CE (55 quid) and the Spear and Jackson SJ-CD18KUK (43)