Ok, this seems about as fair as you can get.
Unlike movies it is now easy to buy music legaly at a fair price online (Â£6.99 per album).
If thats 69p a song, and they shared 9000 songs, each uploaded again say on adverage 10 times (thats a conservative estamate), then Â£4500 (max) is 5p per song, still much less than they would have payed legaly, so really its not a fine at all, its just getting them to pay for what they for each song they stole. If you walked into a shop and stole something and they caught you and said "just pay for it 1/10 of it and we will leave you alone" I would think that great. Of course they stole more then they could afford legaly, and I doubt they would have payed for Â£45,000 worth of music.
Really if they had to pay for it all they would be looking into more like Â£50,000-75,000 per person.