Thanks very much for that Rob, I don't suppose you could PM me a brief write up of what's required. I could really use the extra space. 
Cheers
Chris
Hi,
I wouldn't really say there is a write up - but in terms of what you have to do it's essentially:
1) Remove rear shelf - to gain access to the screw heads fixing the amp tray to the shelf
2) Remove amp from shelf
3) Disconnect sunwoofer connections (green/white + brown white) by unplugging
4) Re-route wiring from under shelf to "suitable location" near filler cap. The large connector will need to be routed behind the O/S boot trim - but there is a route for doing this.
5) Splice cable extensions upto the subwoofers (solder & shrinkwrap please) - using suitable diameter cable
6) Improvise fixing for amp in new location
7) CHECK IT ALL WORKS before you put the shelf back in
Obviously you need to need to be comfortable with working on vehicle electrics and should disconnect battery (don't forget security codes) whilst the work is being done. Removing the shelf isn't my fave job - it's not difficult, but takes a little while and it seems that you are taking half the cabin out to do it.

I'm sure I've forgotten something - but equally sure that someone will correct any errors/oversights.
It's a job for a dry day and would suggest not having any time pressures to finish - just take it steady.
Good luck - Rob