I've bought two so far whilst in Germany - both Triumph and both far cheaper tax free from a German dealer than a UK one. Best thing to do is go to any UK dealer get a tax free price (vast majority will sell tax free) and then see what German dealers will offer you. With the drop in euros to the pound (the usual 1.3ish to 1 down to nigh on 1 to 1) the advantage of buying in Germany may have gone. For example, the new Triumph Scrambler is now over Â£1000 cheaper in the UK than Germany.
There are very few differences between German/UK spec bikes apart from the clocks but this may put you off so maybe you would be better going to a UK dealer.
If you want a really good deal, get an ex-demo (already heavily discounted) tax free and sometimes with only a few hundred miles on it!!!
You will get better help from main dealers than say George whites etc.
I had a Suzuki & a BMW, both from main dealers.
get the euro lights from a dealer in Germany, or Taz motorcycles provided my Gixer lights for about Â£100, they used to tae them off the euro imports