Hey Chris, Ebay is your best bet, there is normally quite a few headlamps for sale both B6 and B7 versions (B7s won't fit your car!). If you've got a cabriolet then you have to buy cabriolet versions whereas Saloon and avant are the same.
I've seen brand new bosch headlamps being sold on ebay for about £50 each. You can even pick up genuine Xenon headlamp assemblies for about £250-£300 a pair with a bit of searching.
Regards,
Andy