[Pidgeonpost]

Thanks. Looked it up in the book and the cover can be removed by 'pressing in the clips and pulling straight out'. The gap between the grill and the bumper cover is virtually zero, but I managed to get a couple of trim removal tools in there. I worked my way along L to R and slowly the grill came away. Clearly someone had been in there before as at least one clip was broken, and I managed to break another, sod it.
I took the fog light out, put a pint or two of water in the bottle, and sure enough it began running out. I had look with a torch, but no sign of where the leak is.
I'm afraid I gave up at this point and booked it in with my indie. I'd have been tempted to go for the bumper off experience, but I need the car available, and I don't have any more spare time at present. I hate giving up but there comes a point...