Id put my money on idle circuit failure in the ECU (Blown capacitors)
Does the Engine warning light work normally?
Worth checking for any codes by bridging the Service connector.
Otherwise could the damp getting in to the ignition side of things. Rotor Arm and distribtor cap have a habit of burning out, so could be a bit of a missfire.
A few things to check as well as the basics - plugs, filters etc. will give more of an idea whats going on.
HTH
Steve M
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Its all gone Norfolk!!!
Now in the Lotus position.