I've used an electric boot release from a E46 BMW (only because it was £10 from the breakers) with an operating button between the number plate lights. It only pops out about an inch when operated, but you are there to catch it if it drops. The wiring to it is only live when the central locking is open and the alarm is off. There is also provision on the lock mechanism for a cable which I have run as a back-up, to the front of the drivers side rear storage bin.
I think the electric lock from the BMW Mini is also doable but have not tried this myself. Making the bracket to mount the lock on the underside of the parcel shelf can be fiddly, I did most of the fabrication with the boot shut and my arms through the back window and the speaker holes. A bit like the proverbial, "Decorating your hall through the letter box".
Looks decent. Have you got any more photos John? That looks like a homemade bracket etc.
Yes, the bracket was the hardest bit. There's three fixings into the parcel shelf. The two tabs at the back bolt to two arms that fix to the shelf and the top rivnut takes a bolt through the shelf. The front rivnut takes a bolt through the top/middle of the gutter around the boot opening where the boot rubber sits. All these seem to give enough triangulation for a steady support.
On the original BMW the lock is fitted to the bootlid and the latch to the car, but this made it difficult to slide items into the boot and complicated the wiring and backup bowden cable. So reversing it makes it look a lot neater.
On the bootlid, the latch just needs a piece of angle to get it to align with the lock.
The one thing that I didn't mention was that the E46 lock wiring included a feed to a boot light which operates when the boot is open. I used this for a light as well as a warning light on the dash to tell me when the boot was open. A bit belt and braces I know, but as it was there it seemed a shame not to use it.
Unfortunately, I don't have any more pictures with it fitted as the shell is now stripped in preparation for a respray.