Hmmm - not easy, this one. I suggest that you get the training school where you intend to do your flying to write to the German civil aviation authority in order to ask:
"Will they accept passes in JAR-FCL PPL(A) papers as issued to Examiners by the UK CAA for the purpose of licence application for a German JAR-FCL PPL(A)?"
If they say "Yes", you have a few choices:
1. Are you able to use the regular PrivatAir Finkenwerder to Filton shuttle? If so, there's a UK Examiner at Filton who could set the exams for you there if the German civil authorities are happy. He's also an Airbus employee.
2. If the German civil authorities agree, you could arrange for a UK Examiner to bring his exam papers over to Hamburg. But you'd need to allow at least a day for the exams and debrief, excluding travelling time.
3. Arrange with a UK flying school to sit the papers there (again, only if the German civil authority are happy) - and take some holiday to go to the UK to do your exams.
Don't forget that all requirements for licence issue including obtaining a medical certificate, must be completed in the state under whose authority the training and testing for the licence are carried out.
Good luck - isn't eurocracy wonderful??!!