I found some corrosion, which when suitable prodded opened up as a small hole in the drivers footwell by my right foot. This hole is elongated and runs alongside the reinforcing plate which meets the main longitudinal box section. Welding in a small plate should fix it, but it occurs to me that some of you souls will have been down this path before, and know where the corrosion trouble spots are on the 740 estate, so that I can check them. Any information would be welcome. Regards Davew ;(