No one sets up a UK registered office unless they enjoy red tape and taxes or cannot avoid it. AOL and eBay who by virtue of their size were obliged to register in the EU have chosen Luxembourg which is the most benign, as far as tax laws are concerned, of the EU countries.
As an aside it is interesting to note that the the standard of living in Luxembourg is among the highest in the world, if not the highest. They also have a falling tax-to-GDP ratio and the lowest rate of VAT in the EU. Instead of trying to emulate their successful policies and learn by them the other EU countries are busy creating regulations and red tape to force Luxembourg to march to the beaurocratic drum and become as burdened by tax as they are.