I didn't manage to find that bit about full download and duration, the BBC site is pretty pathetic the search I did for bbciplayer returned only 3 hits and these were more news/PR with little detail.
At least you can use the ashQuick.exe to scan complete files, this may be preferable.
Assuming that you installed avast! in the default folder, this is the path needed to scan downloads, C:\Program Files\Alwil Software\Avast4\ashQuick.exe