I'd like to do the above but as far as I know I've just got standard OEM headlights with no xenon projector etc... (I've swapped all bulbs for better Philips ones and sidelights for better, brighter LED ones etc...)

I'd like to do a 5W or 55W HID upgrade and someone has said that I'd need the projector style lights to do this; i.e - BMW E38 7 SERIES M SPORT 2 X GENUINE FACTORY XENONS CLEAR HEADLIGHTS | eBay

Is this the case and if so; would these be a direct swap with my current headlights (all wiring/fittings the same etc...)

Otherwise would something like this be a better option:

97-01 BMW E38 Crystal Clear Halo Projector Headlights | eBay

Thanks for any/all advice/options etc...