Re:Re:Strange immobiliser problem

OOOPS! Sorry! Being a newbie, I accidentally posted this in Jimny Chat. Admins please delete that post.

Hello All. 
First post as a new member, though I've been here a few times in the past to look for information. Sorry it's a long post but it might help someone help me, so please bear with me.
I have a Spanish-built 2002 soft-top which has been my daily drive for a good few years. It's getting to the point where the number of repairs needed exceeds its usefulness., but it still runs.
Recently, I was given a 2000 hardtop, which came from a garage whose owner had gone bust. Tidyish, but clearly hadn't been on the road for a while, with a new middle and rear exhaust inside, which I assume was going to be fitted before financial disaster struck. Unfortunately, the keys could not be found, so I ended up drilling out the ignition barrel to remove the steering lock, so we could tow it away. 
At this point, I should explain that I live on a small island, with no access to a Suzuki dealer, or even a locksmith.
Fast forward to this morning. My son, a qualified mechanic, and I decided to try swapping the key barrel, transponder and ecu from my soft top to the "new" hardtop. to see if we could get it going. We started unbolting/unscrewing stuff, only to find that all the parts were substantially different and the plugs and sockets on the two ecu's were incompatible.
Bugger!, we thought, but while we were in there, we put a battery on and my son disconnected the switch from the back of the hardtop's ingnition barrel and gave it a turn with a screwdriver. To our surprise, the engine fired. Another couple of spins and it was up and running, albeit a bit lumpy from stale fuel.
We took it for a spin around the field where it was parked and apart from the bad exhaust and dicky brakes, everything seemed to be working as should. Great! we thought. Let's get it to the garage and have a proper look at those brakes and exhaust. That's when our trouble began. It would not start. We put a gallon of fresh fuel in. It still wouldn't start. My son tried a code reader but it appeared that it wasn't compatible with the car.
The only thing that we had done between having it rnning and the refusal was to press the driver's door lock button a few times.
So cutting to the questions. How come we managed to start and run it with no key or chip? Was it a fluke caused by it standing for a year or more Could operating the locks have woken up the immobiliser? Is there a simple/cheap way of getting it running again/bypassing the immobiliser?
For info, I have the ecu in front of me. I don't know how to do images, so here's what's on the label. (top line) 5H (second line) EC IMB RH (third line) 33920-81A1 2 (fourth line) 081A1 (fifth line)112000-9081 (sixth line) 12V (seventh line) DENSO made in Japan. Below that is a barcode and the number *209081K*
Any help much appreciated.
 
 

Hi Martin,

I'm in Alderney, in the (British) Channel Islands. It's likely that both cars came via the UK.

My son searched around to see if there was a chip stuck on anywhere. That was his first thought when we were able to start it without the key. Nothing found, and that was prior to driving it around. We later checked the footwell and even inside my shoes in case anything had fallen off.
It may be just coincidence, but it started and turned off several times before I pressed the drivers door lock button and activated the central locking. After that, it would turn over but no start.

Quick update:

My son found the list of CEL fault codes for the early Jimny on Rhinopower's site and we have established that it is a code 81 fault, immobiliser code not matched (ECU side).
After much internet trawling for possible solutions, I contacted the Chinese makers of OBDStar scanners, which claim to be able to retrieve the immo code from Jimny ECUs. Glad I did this instead of buying one, because it turns out they only work on the later, OBD2 models.
I've also been in touch with Rhinopower, who replied quickly, and it looks hopeful that he can help me out with my problem. I believe the gent who runs Rhinopower posts here as @Rhinoman.