I found quite a few thanks
I'd rather not loose the boot space to a dedicated sub box so I'm going to be brave and build an MDF enclosure with 10" sub to go in the side compartment under the fuse panel.

One question that I can't find an answer for is where to take the feed from for the sub amp. I think the European spec cars with just the standard business stereo (No NAV/DSP) DON'T have an amp in the boot. I certainly couldn't find mine anywhere around the spare tyre or under the CD changer.
All I could find was a harness with a blue connector under the CD changer but I don't know what its for.