Bandwidth logging by user

[Gavin Westwood <debian-isp@solutium.co.uk>]

Hi.  I've been providing hosting and mail services for about a year now,
and the usage is only now getting high enough that users may be
exceeding their bandwidth allowances.  The problem is that I haven't
been able to find a tool in Debian that will report their combined
usage.  I can work out the http from their website(s) stats, and their
mail usage from adding up Exim, and Courier POP3/IMAP, but it's an
annoying manual process, so I haven't bothered.  Can anyone point me
towards a package/packages that can do this?  Being able to
automatically email on exceeding of allowance would be a plus.

On a separate note I use vsftp for the ftp services, but am finding it
inflexible (e.g. want to have a site with anon read-only access for
downloads, as well as user secured as normal for their own websites). 
Can anyone recommend another more flexible ftp server that still has a
good security record and will be picked up by the stats reporting
package required above?

Thanks

Gavin