Technically speaking a retrofit HID bulb kit would be illegal (at least as far as use on public roads are concerned) as not only would you not have the obligatory self-levelling and washers but given that the original headlamp (including bulb) has been type-approved you'll be fitting a non-compliant bulb thus rendering the whole unit non-compliant.
Of course, in practice, you might not have any trouble (but don't say you weren't warned!
) - it all depends on how attentive your MOT tester is and how man rozzers you inadvertantly blind with badly-adjust lights!
Incidentally, you might think that it is only the method/accuracy of bulb mounting that affects the resulting beam pattern but it's also the fact that HID bulbs have a different shaped light source than the filament found in a 'standard' bulb.
To the OP, if you're simply after a brighter light output you could always just upgrade your standard filament bulbs - [1] have done a number of product tests for various types (standard, +30% and +50%) so take your pick! Much cheaper, no retrofitting and legal too!
Mathew
[1] After reading a few reviews it'll ask you to register - just clear your cookies and hit reload... it'll think you're a new reader again!
