Try the crank sensor BUT my money would be on the loom plugs below the N/S bonnet vent.... IF they are still there, cut the loom plugs off and solder it all together...
This job, as unpleasent as it seems is a must for an escos owner and is on my list (Damo gave me that advice last year and I still have'nt got round to it.
), in the mean time try disconnecting the plugs, cleaning and reconnecting them with lots of grease.