There ARE cheaper ones BUT!! they are being sold as individual sides (Left or Right) and that is a minefield!! as you would have to know that they were compatible with each other ie. Xenon, non-adaptive, EU Spec, etc. etc.
You should be able to get the Tax Off and when it comes to re-sell get some of your money back.
The OTHER!!?!! alternative is set your UK lights up using the adjusters to form a beam that is almost!??! LHD pattern, someone had done it to my lights to get it through an MOT when it was UK registered. but the xenon fixture looks like it is cross-eyed optically and wether the BFG inspectors are wise to it????????? Probably:sarcastic
Dunk