Hi Wozzie,
Taking a dog from UK to Continental Europe is no biggie...just need current international health cert + proof of rabies vaccination. We brought ours over from the US without any trouble. Just check with your vet to make certain nothing has changed. Oh, you'll be glad to know, that Boxers are not on any restricted "Dangerous Dogs" lists here in Germany.
I live in the Kaiserslautern area and there are quite a few Boxers that show up in the papers which need rehoming. There's also a Tierheim (Animal shelter) which seems to have the larger breeds. US military Vets also run an animal shelter for pet adoption.
Unfortunately, there does seem to be a general reputation that military here in Germany (regardless of originating country/branch) has a tendency to rehome or abandon pets. :( It's sad, but every PCS season, there are lots of ads running to find homes for pets... usually the larger breeds.
Do you know where you plan to be stationed???? There's a large contingency of Canadian + British Forces here in this area. I know Lahr has closed down -- too bad if you like Europa Park ;)
toodles