@Chris don't confuse my meanderings on this thread for any urgency on my part to do anything. It really isn't a priority at the moment and I'd imagine any chemical solution would work better when the weather is warmer and drier anyway.
no, i haven't Simon, can't see anything to cause confusion? - but you helped "throw down the gauntlet" though, otherwise i wouldn't have bit, so i'm up for above challenge wherever it leads now you've "put the fuel on the fire".