Went to tension the aircon belt due to it being a little squeaky, and the f***ing plastic adjuster thing split. At least my local dealer had one in stock, and at a very reasonable price. Always makes me laugh how variable the pricing can be on random little OEM bits.

Yup you are correct I just didn’t have the time to check when I had the bonnet up, was easy to check the middle wire feed in situe    when ac comes on revs go low for a second then back up to normal, same with when radiator fans kick on. It’s working normally, it just faults after deceleration- I’m thinking it might just be gummed up inside the actual IAC valve but the spinny thing on top moves freely when I remove the sensor. Parry spares has a whole IAC so I’m gonna order that regardless as I’d like a spare 

Don’t you measure resistance on the iac solenoid pins to see if the coils  are still intact and measure the same. also if you still have AC what happens when you turn it on, Does it still idle faster and slower again when AC off.

Hmmm yeah not sure, when car is on the IAC sensor receives 13.8v on the middle wire which is normal I think. It only faults when I decelerate for a long period (I.e down a hill) then it goes into low power when I accelerate more than half throttle the first time after the deceleration, then the check light turns off and it drives fire until the next deceleration 

Time to pull out the multi meter and measure resistances. But doesn’t the IAC share some wiring with the o2 sensor maybe the old sensor blew a fuse or one of the ignition relays.