A year abroad is not a compulsory part of Joint Honours German. However, it is very strongly advised, and an aspect of languages degrees particularly valued by employers.
In fact, virtually all students taking Joint Honours German do in fact spend a year abroad during their course. This may be in the second or third year.
It can be spent at a German-speaking University: there are exchanges with Köln, Göttingen and Konstanz. Other students take a year out and work in Germany or Austria e.g. as language assistants in schools or find a commercial placement.