Thanks - its kept outside, but on the flat. I could not get the water to leak back out when I waved it about, so could not find the point of ingress. Had to drill holes in the base to drain it, which are now taped up. I did seal the back lower lip (base to lens join) with silicone in the hopes of keeping the water out, only time will tell if that makes any difference - I’m not optimistic.
Are the scuttle grommets the silly plastic clips which retain the plastic ‘cowl’ on the windscreen (that covers the wiper motors), with their feeble foam seals? If so, I have done both mine (last year) and my daughter’s (last week). An irritating fault, but what bliss to be able to drive without a plant tray in the passenger footwell! I would have had to fix mine quicker if it had been the driver’s side.