Glad you found it easy Andrew.
With regards to the tweeters, they are a funny rectangular shape, so i would be very very surprised if you could find anything to repace them. Plus i had mine wired up to my old system and they lasted about a week before they popped anyway.
I did put some Sony tweeters in, and my goodness did they make a difference. You can see them mounted just to the right of the steering wheel-one each side obviously.
Tweeters. I'd def recomend them if anybody's considering it.
@Weeksy. Depends. If you just want to upgrade the speakers in the doors, then just replacing them is fine. I'd advise using the speaker wire that comes with the speakers as the Volvo wires will be rated to work with their speakers. Basically, if the signal going through the standard wires is too great, then it will filter out the frequencies it thinks the speakers can't handle....and as the car isn't alive, it will still think the originals are in so the sound quality won't be as good.
If you want amps etc, thats a whole new ball game. You'll need a new CD player for a start, then it's just £££. But if you love your tunes, you won't regret it.
I didn't!