So my boot wouldn't open, MK5 Astra just out of warranty.
In the run up to it failing it had become difficult to open, needing to press very hard on the handle.
Having read other threads I checked all the other rear electrical components were working, so no fuses blown.
There was no click when I pressed the button, so looked like a switch fault rather than solenoid.
First problem, how to get the boot open. One thread said to start taking all the trim off, but I found an easier way.
On the inside of the boot there is a little rubber cap. I couldn't get it out so I pushed it into the boot trim (you can recover it later).
Inside you can insert the extension piece of a socket set, direct into the centre of the lock mechanism. Rotate gently and the lock opens.
Now remove the plastic around the catch, couple of screws.
Now remove the boot lining. A few of those annoying plastic catches which pull out with a bit of force. It is possible to get it off and back on again without removing the plastic on either side of the screen.
You can now recover the rubber cap if you pushed it in.
Now undo the nuts holding the silver strip on the outside of the boot, this should release the strip and the switch.
Disconnect the cable where it goes through the body work.
Now remove the switch housing from the silver strip, the rubber pad you press can be eased off.
Temporarily connect the wiring. Check you can close and open the boot so you know the switch and wiring are fine - mine was.
You should find the microswitch is held in a slot in the plastic housing.
What I found is the switch is held in place with a splurge of hot glue. After three years the glue has gone hard and cracked, so the switch has moved back in the slot, so no longer works.
Push the switch fully into the slot and put a bit of superglue on it.
Once the glue is set reassemble in reverse order.
Took about an hour from start to finish. Has now been working fine for a couple of months. No cost to fix either.
If only all the other examples of poor build quality could be fixed so easily. ;-)