Hi Builtolast and others.
Just wanted to let people with similar issues know that my van is all sorted and happy once again.
It was quite an ordeal.
I took it to an Auto Transmission/Electrical guy who was highly recommended to me, without success, as I said in my original post.
Then, based on this forum, I decided to remove the ECU and get it looked at. I was impressed with myself that I was able to a. find it and b. remove it.
(the ECU looked so pristine in condition that it was hard to believe there could be a fault in there, but I guess that it's been neatly sealed away from the rough and tumble of the world for 20 years....)
I could have taken it to Injectronics which is quite near me in Victoria, or post it to the mob in Sydney that get a few really good mentions on this forum.
Turns out Injectronics don't deal with the general public. You have to send it via a business like Burson, or my Auto Electrical guy, then they Bill that company and pass it on to you. So I think there is a middle man cost. -it all seemed a bit messy.
I decide to post to the guys in Sydney and they were awesome.
Dropped in the post office 10.30 Wednesday and by 11.30 Friday it had arrived back at my house!!
While it was there, I spoke to Antony (via phone) and he said that there were 2 capacitors that were leaking and this would be exactly consistent with the problems I was experiencing.
Reinstalled it and all is good.
-2 leaking Capacitors had to be replaced, total $345 including all postage etc.
Highly recommend these guys.
Thanks for your interest and responses.