For the sake of completeness....
You could always find a German FE(A) and elect to revalidate by 'test' prior to expiry. He notifies the CAA by email, does the flight and then also sign the paperwork for you there and then. A slightly more expensive way of doing things - but perhaps a tidier solution all round.
Renewal can also be done by a German or any other EASA FE(A) who could then sign the certificate. The main difference is after expiry the examiner would need a 'certificate of assessment/training' from an ATO before undertaking the test.
HTH
DD