I've asked this question myself, and was basically told, if money is an issue, just get the Driving Force PRO wheel. It lacks a clutch pedal and only has a sequential gearstick instead of a 6-speed but apparently the wheel itself is very good. I've seen them as cheap as £70, but i hear you can get em for £60 (haven't ever seen one that cheap).
I haven't got either yet, but i've sided with the force pro wheel, i just can't justify £140 for a wheel, for an extra £20 i could buy a 360.