Gosh that does all sound difficult.
Would be great if someone in the workshop had been involved in renovating a double brick home.
Can you get into the ceiling to bring power into the rooms?
I know there is still the problem of the double brick though even if you CAN get the cables down the walls but I suspect you cant??
First thing that comes to mind to me is, what if you put all your power in on the outside of the walls in conduit like you said you already have in the old part of the home inside and pack out the walls 20mm to cover all the conduit and then re-plaster, it means you would reduce the room by a little bit but it could be a way to get all the power points in and perhaps use something suitable with the packing material to attach the power points and light switch brackets on to?
When we built, albeit on stumps so easy enough to get under the house, we were adamant that there would be little or next to zero entry from under the house into the house to limit any rodent infestation. Unfortunately we did have to put a couple water outlets through the floor and one power point but I have bogged up every possible hole under the house with No More Skills as my plasterer calls it or No More Gaps if you go the Bunning's to get it ha-ha
If you do have to go under the house I would recommend you put all the power cables in conduit to prevent rodents from chewing the wires firstly but the conduit can be brought into the home neatly with a perfectly round hole however, if you have double brick then I don't know if there is an internal timber frame like a brick veneer home has, I suspect not?
A dilemma I will have to think more about ha-ha
Unfortunately most of the house is 9" double brick and powerpoints (most of which donlt even work) have been installed down walls without being concealed. I'm going to see if they can be brought up through the floor.
Double brick wall normally they will run power cables from the top using a cable feeder, my place the wall was capped so they have to drill through that as well to run cables.
You will need to check how the foundations were done to run cables up from the floor, hard to do if they have laid a slab.
Hope all is well. Just wondering how your renovation is going? It would be great to get an update.
Feel free to post post anytime you need a hand.