As I understand things:
New items manufactured in the EU are not subject to import duty.
You only pay VAT once, so the supplier should either do the admin for UK VAT or sell it to you VAT-free and you have to pay UK VAT.
Actually, UK VAT is 20% whereas German is 19%, so it should be slightly more expensive than retail in Germany.
If the seller doesn't do the VAT for you then the courier will likely do it on your behalf and charge you a fee for it.
Your shipping fee should be VAT-inclusive.
So, overall your extras will be shipping, 1% higher UK VAT, and a shippers fee for doing the VAT (maybe £20?).