Stupid Mistake - No possible easy solution.

oh my....i have no idea... is your boot carpet in the boot? you could go up from the bottom to hide cuts/welds if no boot carpet. good luck mate

Hi
I feel for you and I hope you get it open without having to resort any cutting.
I assume that you can see through the lock barrel  into the boot. I purchased an ingenious piece of equipment called an auto inspection camera. This is very much like an endoscope that doctors use to look down a persons throat. It should be small enough to insert through the barrel hole and with this you can see inside the boot as it has 2 led lights. You can probably put a wire through at the same time and hopefully hook the boot release and open the boot.
Good luck 

Called a friend of a locksmith - he  came out (mainly to laugh at my scenario) but did say because there isnt a lock so he can do much.
 
Tried the mechanism on drivers side floor - simply wont work as it relies the lock mechanism to be in a firm position (ie bolted to rear beaver panel)
 
I did try and hook something onto the latch through the key hole but there is no way I can do that and then pull it to release.
No boot carpet but not sure what you meant sorry.

Sounds like you will do some serious damage to the bootlid.  unless you are in a desperate hurry, dont rush it.
 
if you can hook something through the key hole, and then hold it stiff, the interior release may work?
 
or
would this work?:  Open engine lid, then you should be able to see the boot hinges.  cut them (dont think you will be able to get to the bolts), and this may give you enough space to lift the forward edge of the boot and get in there, or reach in with your hand?
 

other way, if exhaust was off, remove the heat shield between exhaust and boot floor, theres a few largeish grommets, pop one off, go in.

theres heaps of ways, if you have a work car like mine full of tools to hook wires (clothes hanger wire, rods, hook springs, flexable inspection cameras ect) its easy! no damage needed. If you were vic, ill pop it open 

WIDEMR: that sounds promising - when you say large grommets - enough to get a hand in - all will is still be working with wire on a cord?

chase_d
Hopefully the mechanism doesn't have to be rock solid (ie held like it is bolted in) as I think thats going to be be impossible to hold it that tight.

 
which part is loose? the latch or the lock barrel assy?