Oh, New London doesn't have a lot of abandoned properties -- they're either occupied or they've been removed, at this point.

Outlying areas, on the other hand -- there was a whole abandoned muggle village, near where I grew up. But those wouldn't have the floo. We could floo straight to Pansy's house and wouldn't need anyone to apparate us.

About the Fidelius -- Professor Dolohov has books on absolutely everything and given that he spent today talking about cooperative magic and ritual magic and all that, I could ask him about the Fidelius Charm without it being the least bit suspicious.