ok, I've done some of my own digging
concert pack is:
Bassworks + Co-axial speakers in the front complete with speaker rings (and mine say bassworks on these rings, just to confuse matters!)
Bassworks is:
new speakers (not co-axial) in the rear + amp
may or may not include speaker rings.
So - I guess I've got the right bits - but it still leaves me with lesser (?) speakers in the rear - which is where I actually need the better quality ones to cope with the increased volume daughter wants...
BUT, according to the site, you can't combine the co-axial speakers (which withOUT bassworks can go either front or rear) with the bassworks system
Possibly becuase they are 4ohm, whereas bassworks speakers are 2ohm?