A friend at work showed a rather good tool for viewing filesystem usage, called WinDirStat. It did seem to have the edge on the KDE program I used for this purpose - Filelight. Then I discovered that it was a clone of...a KDE program!
So, a quick apt-get install kdirstat later and I've trying it out on KDE. WinDirStat has, admittedly, made some improvements - in particular being able to break the files down by file type, which KDirStat doesn't have yet. Apart from that, and differences relating to OS, it's pretty much identical - right down to the little pac man who chomps backwards and forwards as he trawls through your files.
Here's a screen shot of the KDE app — it is nice looking as well as a very useful (as always — almost all of the people I've introduced to KDE have spontaneously commented, with genuine admiration, about how nice it looks).
Yes, I do have 300,000 plus files in my home dir :-)
I was bragging to my mate at work how well KDE does network transparency using kio-slaves, and, yes indeed, KDirStat can analyse FTP sites, zip files, webdav:/, fish:/ (and everything else) in just the same way. Lovely.
OK, that's enough KDE worshipping for one day :-)