That "o" ring mod is not for uk lights, i have S4 xenons in mine and they are a completely different light, from memory the "bi" xenons have the "o" ring. As for standard headlights try removing the grey vents that are on the underside of the headlight, this allows more air to flow round on the inside of the light also check the rear bulb covers for a tight seal, you could also try blocking the grey vents up alltogether as sometimes this can help, the problem with the xenons is the lower wattage bulbs coupled togethr with the ever more common use of led side lights doesn't generate enough heat to burn off any condensation. ( so my local dealers tell me),