I finally found a complete spare wheel on eBay and received it yesterday.
So the process was:
I removed the foam thing filling the wheel well
Put the compressor and foam plus another compressor in the compartments in the boot sides.
Then I removed the valve core to fully flatten the spare wheel.
Re inserted the valve core.
Used a bit of wiggling to get the wheel into the well.
Used the plastic screw thing that comes as standard to screw the wheel down.
Put the carpeted boot floor back and put all the left over bits in the loft.
Have a drink and congratulate myself on a job well done

I would say it's a very tight fit and the wheel protrudes a little above the plastic boot floor so I couldn't use the plastic wheel well cover so the only question I have left is as this cover isn't in place now and just the carpeted boot floor am I now exposing the interior of the car to anything nasty from the battery? The plastic cover wasn't exactly air tight so I can't see any issues?
Other than that it's all good and happy to have a spare on board in the land of pot holes!