swapped my factory fit Philips H7 55W long life bulbs for Phillips extreme power - £22 a set off ebay.
Not made much difference to be honest - i'm having my headlight beam alignment checked this week as currently at times the lack of illumination is downright dangerous on unlit country roads.
An MOT tester on another forum tested a load of bulbs on the testing machine - Philips Extreme Power and Osram Nightbreakers gave very similar overall light levels, and about 30% up on a standard bulb (not the claimed 80-90% from the manufacturers, but they may claim their figures at a certain distance whereas the MOT is at 1m or less ). The one bulb that did stand out far beyond anything else is the relatively cheap Ring XenonMax.
Fitting xenon kits, even the non glar filtered version from
www.hids4u.co.uk are illegal - you may not fail an mot, but the Dept for Transport have isued guidelines on their use and deemed them illegal.