Twas the FITV
Can't believe I didn't test this sooner! 
I was adamant it was the IACV from the start, which is understandable, but had I simply stuck my finger on the blinking FITV port in the throttle body then I could have saved myself £60 buying a replacement IACV. Well at least the only other expense was the fuel filter and injector cleaner, but those are things I would have bought anyway.Anyway, sorting the FITV wasn't as easy as it should have been. Basically I established it was the FITV as when I stuck my finger over the lower hole in the throttle bottle whilst it was surging it then idled perfectly. The FITV is located right at the back of the inlet manifold, with the cap I needed to remove conveniently facing up. First trouble was that the cap was held down by two posi-drive screws, and of course these wouldn't budge and started to round off. Simple solution... Drill them out. With the remainder thread under no load they unwound with no effort. So I'm in! Now I have a retaining plastic collar that screws up and down the inside of the FITV body. This collar forms the female part of a valve. The male portion of the valve is sprung and is pushed up from below when the engine warms up. I basically need to wind the female portion further down to help close the valve up when it's warm. Mine could indeed be wound further down
I wound it down fully, put the cap back on. Started the car, let her warm up and perfect! No surging Went in for tea 
Then after tea I went for another spin. Got to the bottom of the road... And it's still doing it
Although it is much improved. Ok, so it's off to Dad's garage again. I remove the cap again and this time remove all the gubbings to give it a good clean with carb cleaner. I detach the body from the back of the inlet manifold too to blast some carb cleaner through it and clean it out. Fortunately I don't have to detach either of the coolant hoses to do this. I also cut two new grooves in the top of the retaining collar as the original are useable for unscrewing/screwing it, but they're starting to look a bit messy (I clean these up too). Then once everything is clean, I reassemble and try again. It warms up and sounds great, idling perfectly. So I go to reverse the car out the garage, but as soon as I blip the throttle she starts surging again. This time I remove the cap whilst the engine's still running (It's safe to do this). I place my finger over the hole in the retaining collar (the female part of the valve) and the idle smooths out again. I remove my finger and it remains perfect, then I just touch the throttle body enough to raise it a few revs and she starts surging again. This tells me the valve simply isn't strong enough to close the valve up enough. So I go back to my Dad's work bench and have a rummage. I'm looking for something that sits in the bottom of the FITV body on the small pin that pushes up, but it has to be a little larger in diameter than a 5 pence piece so it spans the underside of the gubbins and doesn't fall off the pin. I shake Dad's "washer jar" about a bit, then have a further rummage around his cluttered work bench and in his scrap metal bin. I go to give his washer jar one last shake and there it is... A small 10-12mm diametered little pressed dome with a dimple in the top of it. God knows what it is, but it'll do! I compress it a little flatter in the vice, then drop it dimple down over the pin so it locates, and then the base of it is facing up so that it spans the underside of the FITV gubbins. I drop the gubbings in on top and screw down the retaining collar and start her up. Let her warm up, then blip the throttle, then rev her properly a bit and she seems perfect
Put the cap back on and go on my way. Done a couple of miles tonight since and she's smashing Sorted! 
I no longer feel embarrassed to be stopped at junctions... Now I feel cool
lol.Just one last annoying thing to sort, which is the offside rear disc rubbing every revolution, which could be the disc has warped (although it was fine on the Aerodeck before the crash
), or it simply isn't sitting on the hub properly. Either way I'll swap back the disc that came on the car to see if that's the same to establish if it's the disc or not.I've got Thursday and Friday off work this week to finish off a few niggles and to finally clean the car inside and out... Now that she deserves it
All in preparation for her getting restored to her former glory and some over the next couple weeks Sorry that was my usual drivel, I can't be assed to proof read it either, so I'll simply apologise if something doesn't read right
EDIT: Proof read
