In the event that the UK leaves the EU without a deal, you will still be able to drive in Germany using your valid UK driving licence under the SOFA. However, to drive in the rest of Europe, you will need an International Driving Permit (IDP).
IDPs can be purchased from your local BFPO from 21st March 2019. IDPs will be issued following the same process as the UK: you will need your full valid UK driving licence, a passport sized photograph, and your valid passport as proof of identification if you are presenting an older paper version licence.
The IDP will cost approximately €6.50 (depending on FFR) and serving personnel will be able to claim this back.
Priority for issue will be: operational need, travel for courses, compassionate travel, and travel for leave.
To prevent excessive queues at post office counters, if you do not need to leave Germany before or during Easter, it is recommended that you postpone your application until May.