hi, i did budapest to normande (france) a few years ago. I didn't rent bikes but i did manage to pick up some great maps. There called cycline and they do that exact route. To be honest, that section was definatly one of the highlits of the trip. simply fantastic cycling and great places to stay/drink/just chill and have fun. There's a savage hotel along the way which has to be one of the oddest buildings i've seen in a while. I think it was in passau but i'm not sure. i'll give you the name of it if i can think of it. give us a shout if you need anymore info. i have a diary but i never managed to get it in type form.

Edit: It was called the Rotel Motel, it's in passau and specifically for cyclists. so good craic if nothing else