wiredsoftware

In case it helps anyone in the future, I managed to get the CD changer out by taking two old credit cards, chopping them down to two thirds their original height, and shoving them in either side. This is enough to push in the little lugs and pop the changer out. 
 
The lug on the right of the CDC can actually be pushed in with your finger as there is a hole on that side of the rack, but the one on the left has no hole so you need to insert the card on the left for sure.
 

Got this working today. For the benefit of anyone else who may try this:

- Get a standard 12v automotive relay.
- Connect pin 86 to the red+black wire on the RClick unit.
- Connect pins 85 and 87 to earth.
- Connect pin 30 to the red+green wire that is in the smaller of the two red connector blocks on the control unit in the car. This is the wire that leads to the boot release handle button on the boot itself.
 
Job done. You need to hold the button on the remote for ~3 seconds and then the boot will pop undone.
 
If you are using a 5-prong relay (one that includes a pin 87a), just leave that one unconnected, you could have used a 4-prong one instead but it won't do any harm.

Found it, the wire that's brown with red stripe on connector A to the head unit is switched with the ignition.

All sorted. Switch was faulty, no response across it on the multimeter when pressed, replaced and all is fine.

The fuse had blown, washer was working fine.
 
Solved this now, thanks all. I had the motor apart and there was lots of corrosion, guess the washer pipe leaked at some point or rainwater got past the seal from the outside. Fitted a secondhand motor from a breakers (£15), and it's fine now.