I had a crack last night and have this basically finished now. The format string will go in the config.ini section in the form of something like:

%a - %n - %t (%y)

Would give:
Joe Satriani - 3 - Surfing With The Alien (1987)

At the moment there is only support for
track number (not zero padded)
title
album
year
artist

Anything others that people want?

The track number is a problem. ID3v2 supports more than two characters and some rippers (like CDex) put the track number as 1/11, 2/11 upto 11/11 in the v2 tag and simply 1, 2 .. 11 in the V1 tag.

Comments?