Perhaps a bit late to this thread!
tbn3 - When you say you can find lots of headlight units but won't pass the MOT, which units exactly have you found? I've just found an ebay seller with 2 separate listings for £45 + £12 delivery, so a total of £114. To ensure you look for the right items, look on this original BMW parts number site called 'Realoem'. http://www.realoem.com/bmw/enUS/select
You can plug in the details for a UK car and browse to get a hold of the part numbers for the RHD headlights. Once you have that, you can filter your searches to find RHD spec headlights.
Camoscato - Thanks for the kind words! I do remember you from the 5 forum some years back! An update for you, on the E39 (perhaps other models too) the little internal switch isn't a 'full' solution. It's meant as a temporary one so that when the car goes to a country with opposite side driving, you can aim the beam a little to the other direction to prevent dazzling, however the movement isn't 'far' enough as it were so a portion of the road remains unlit. There are indeed 'LHD' and 'RHD' versions of the headlamps and for full light dispersion, the correct ones should be fitted.
KFDancer - The E60 M5 is an awesome performance car and I'm sure you got to revel in the sound of that V10 and the drive of the car itself! I've not owned the model you had, but I *really* want the Touring version of it if I ever got one. I do have an older 99 year M5 tucked away though and love the driving experience! That small fuel tank and the V10's potential thirst, especially with my 'spirited' driving when in 'M' mode isn't fun though like you say - but when you are out driving, you kind of forget the financial costs
Cheers, DtM! West London & Slough UK!