The bad news - it was only one little pipe that had been mis-routed (the vacuum pipe from the Manifold Air Pressure sensor) and a lack of fuel in the tank that was causing the problem - so I could have saved myself all the cost of the parts listed above PLUS the £116 (labour and £20 in petrol) that my friendly garage charged me - if only I'd known what I was looking at / for
ah well, que-sera!
Next job is getting the sill / lower arch repaired and then MOT and (with any luck) back on the road!! Wooo-hooooo!!!
Thanks for all your help!