ok ok
the series 2 had 2 choices, H1 55W for the povvo models and Xenon D2R 35W (±4300K?) for the others, the reason they are a lower wattage is you get a lot more light from a xenon than a halogen. I'm guessing if you put a 55w xenon bulb in there it would tax your system and blow a fuse.
Parkers: Series 2 use a very common T10 fitment. The best thing to fit here would be a LED. there are plenty on the market but I suggest you stay away from the cheap ones. I use Carmate and have not seen better.