O.K. guys - some of the problems listed were not to do with the spring, but to do with the Merc being parked up with the head off for 4 months. The E<>S switch on the Auto transmission console must have got dirt on the contacts as did the 'kick-down' - so I now have full operation of both standard mode and economy mode with operational kick-down.
However, cold - start is still not operating and I have the 'no throttle' effect at half-throttle or levelling off once speed is reached - I assume this must be due to this spring.
I am waiting for the Techie to bring round the spring and I will upload a picture of it (alongside a ruler for size etc.)
Thanks for looking and commenting, any help is greatly appreciated.