How low can I legally go?
As low as you want as far as i know, only thing you have to do is be able to get on to the brake test things at MOT centres
How low do most people go?
Micra 35mm
What do I need? New shocks or springs?
Can be done just with lowered springs on standard shocks, 35mm that is
Any more and you'll be looking at coil overs!
How much am I looking at? £££
Set of lowered springs brand new you'll EASILY get change from £100
Coilovers £600 PLUS!!