I've now tested:

BulletProof FTP client - This one is from the same people who make BulletProof FTP server, which I use for FTP servers. It isn't free, and is quite a basic FTP client. It doesn't allow multiple connections, or tabs, and it has now directory tree navigation. However it is the fastest FTP client I've found and it loads up the image directories from CA's FTP really quickly, so is great for navigating and uploading files.

ALFTP - Now this is a very strange program. It is free and seems to have a few features. However it isn't easy to work out how to get it to work. If you access an ftp server it says it is connected but doesn't retrieve any directory listings. Shame it doesn't work too well as it does have directlry tree navigation.