The OEM thermostat is still seems to be running better, temp still dips a little but is a lot more consistent. There's a few little hickups that crop up under different throttle loads, but I'm hoping the new manual ECU should resolved those. 
 
Now onto the fun and games while I work out whether my SCer or water pump is squeaking and rattling. I'll probably just keep running it until which ever it is dies now then chuck in a spare.
 
Thanks again!

Yeah took me a couple of hours to copy the old pulley guide and used an old 3s cam belt pulley. Finally had it running longer than around the block and experienced the infamous interwarmer's effects. With the belt really tight it sounds ok but theres a bit of a bearing rattle/squeek which I'm assuming is the SCer but I'm rebuilding a spare at the moment so it shouldn't be a drama. 
 
My manual ECU arrives Friday so fingers crossed its all ok and might smooth things out even more.
 
Over all its running pretty well, an absolute dog if its sitting at the lights but gets going after that and a little bit rough through 2,000-3,000 while its cold but its no where near as bad as it was.
 
Back to rebuilding the suspension and fixing a few other body things then its all sorted!