Are you sure about that? Sorry for the weird question. The UK lets me enter the country with my German ID card ("Personalausweis") fine. It does seem a little odd that Germany would refuse UK citizens to enter with a similar ID card.
Don't forget that most UK citizens don't have ID cards QS - in fact, when I attempted to get one I was told that I couldn't as I was British and I had a passport
Driving licences aren't machine readable as far as I know, so I'm reasonably sure you'd need a passport for Germany. I caertainly have every time, as the UK has never offered a viable alternative
Don't forget even if Germany will let you enter the uk border control won't let you leave the uk without the proper documents and that's usually a passport only uk internal flights will accept uk driving licences or military ID cards