Iain, the map you're looking for is available from the catchily-titled
Bayerische Landesamt für Vermessung und Geoinformation. From the menu, select "GeoDatenOnline". Then select "BayernViewer Plus". Then select "Start". Then select "Starten". Then click "Anmelden". And you're off!
Hey, it's got 'Amt' in the title - you didn't expect it to be straightforward, did you?
What you eventually get are the excellent Bavarian State maps, with the ability to switch between map and aerial photograph view. So it's a bit like
Google Maps, except that it's been around for a decade and the map actually marks things

Just to add to the general chorus, Kompass maps are indeed rubbish. In some areas they have larger-scale maps, eg. 1:35,000. But all they've done is enlarged the 1:50,000 map - there isn't a single piece of extra detail!
For Bavaria, the best maps are the Bayerischeblahblahamt topographical maps:

For Austria, the
Alpenverein maps are best -- for the areas they don't cover, you're fucked.
Of course, the best maps in the world come from
Southampton