Seems, fingers crossed, that i'ved sorted it. Gonna regret saying that I know. Had a proper old wiggle of the wires,.. then some more, then some more. My mate who works for Bridges Renault in Newbury rang me, so I asked him his view. He said wires under the seat; the wires that are connected at the multi-connector, as are the pre-tensioners. However he said you can't solder it yourself as the risk of the airbag deploying without being disabled first was pretty high! Renault charge an hours labour/£77.
So I wiggled some more, then got my can of lighter fuel on a rag and wiggled and cleaned, cleaned and wiggled. Seems to be ok now... We'll see how long it lasts though.
Thanks to all the help I received.
John