So spend a bit of time (Having had a good night's sleep so with a clear head) working on the twin today.
Happy to report that I found the problem - both decompression valves were stuck solid open. These have now been replaced and I have 40 psi compression.
5 pulls and away it went.
It did die after 3 seconds and backfire quite badly though. I will have to wait until I can get a new diaphragm cap as I snapped the inlet off when removing the breather hose. I also want to replace the diaphragm itself as it is less than perfect and the ignition/kill wires as they. Once I do all this I will try start it again and see what happens. Once I fix all the issues I KNOW about I can find what else is going on with it.
Thanks for your assistance Blumbly.
Pete
