Also see: Lowering, which focuses on B110, but most information is also applicable to B210.
Using B110 strut tops in a 120Y lowers the front by 1 1/2". The PCD is different (slightly) so I knocked the studs out, elongated the holes with a die grinder, put the 120Y studs in. Gave them a zzzap to stop the moving during assembly. The hole the in the B210 strut tower needs to be opened up, I used a set of vice grips. Went a little at a time, about 4 times around.
120Y lowering on the cheap
07/06/2013 update by L18_B110: I just fitted a set of B110 strut tops to a B210 and found it slightly different to the above info. PCD is identical - no mods required there. The B110 studs fit straight into the B210 holes. B110 studs are smaller diametre, M8 versus B210 studs M10 but that's no problem. I just used a washer under the nuts. The centre hole in the B210 strut tower does need to be opened up from 80mm diametre to 94mm. I cut it carefully with an angle grinder with a thin cutting disc after marking around the opening. This mod lowered my car approximately 30mm.