ACE in Germany are much cheaper than ADAC and they cover Europe too. I used to be with ADAC and have been with ACE for the past 4 yrs. I believe you will need a German address for both (at least for the ACE) but I know that ACE will accept a British licence plate (it's you that's insured, not the car).

If you are under 30 yrs you pay EUR 28.75 for the first year, EUR 57.50 thereafter and also if you are over 30 yrs.

http://www.ace-online.de/cps/rde/xchg/SID-53EEFEFA-ADD18CD7/ace_internet_new/hs.xsl/24_10830_DEU_xHTML.htm

ADAC membership is EUR 79.50.

http://www.adac.de/mitgliedschaft_leistungen/mitgliedschaftstarife/plus-tarife.asp?ComponentID=210118&SourcePageID=209016&MGTMode=2