Whack the bolt in the knock sensor with something at idle. the revs will change if it's working. Disconnect it at the plug and make sure none of the wires inside are shorted together or shorted to the screen around the cable.
yeah its ****ty - but can I not disconnect it or bypass somehow just for testing - will do a bit of googling for this or if you know (it definitely needs replacing)

Not sure which way the switches go without a diagram in front of me. As long as they change state, open to close or vice versa, I'd be pretty confident they are working.
Yep all good here

The hunting, if at idle would definitely be the the ISV but I don't recall seeing one do it mid range. Have really good look for air leaks. Spray some WD40 or similar over the pipe work and see if it revs up differently at idle.
agreed

I just went out there then and held at constant revs and listened to the injectors, I can hear them cut out and back in again only after getting past about 2000rpm all the way up and only when holding steady throttle position - now knock sensor doesnt cut fuel right??? just retards ignition timing???

I really like this little car and it has been so faithful -

Courtney