Does sound like it might be your brakes.
Whip the calliper off, give the slider pins for the calliper a good clean - remove any black / carbon deposits from them, grease them and re-apply. Also make sure you grease the back of the pads with copper grease - this tends to stop them singing too.
It tends to be that the inside pad on the brake calipers wears much quicker than the outside pad, owing to the piston applying the braking force to the inside pad, so you may find if you inspect the brake pads that the inside pad is actually worn fairly close to the end of its life, so worth checking that too.
It could even be tyre squeal possibly if your wheel alignment has gone out, although it doesn't sound like it. Because when you turn left for example the inner edge of the O-S-F tyre turns a tighter circle than the outer edge. Likewise the N-S-F outer endge turns a tighter circle than the inner edge. This is reversed for a right hand bend. Typically tyres don't tend to complain about this but if the alignment was out they could. I don't think by reading your description that is the case here though but if all else fails.
1999 156 1.8TS Sport Pack 3
2001 166 3.0 V6 24V Super
2003 156 GTA 3.2 V6 24V
2005 156 1.9 JTDM-Jet Sport
2008 159 1.9 JTDM Lusso
1997 GTV 2.0TS Lusso
2001 147 1.6TS Lusso