Confused by headlamp options (N00b FTW)

[Thom]

I'm not sure about the options I have for upgrading my headlamps (2002 1.2) so I thought I'd ask. (Most probably the biggest n00b question ever)

I know that I can upgrade to HID. Is this legal with my headlights or do I need complete new units?
What other options are there to improve the headlamps rather than HID as well?

Cheers