I think I might have found the answer. On the Kennet I have chucked in two quarters of the big fat dog food sausages (bought in supermarkets) and about a pint of wheat above my swim.
The signals are attracted by the smell of the dog sausage and then they are occupied with the wheat. I have tried both downstream and upstream of my swim but this is too much, just upstream works fine. It does not totally resolve the problem but at least it makes the fishing tolerable.
Over the last couple of weeks the water temperature has decreased from upper 60s F to yesterday when it was 52F. Obviously signal activity is reduced in cooler water but the above method does work.
Only pitfall is that the swim upstream is now full of crayfish. Where I fish there is rarely another angler but on busy waters this method might cause problems with other anglers .....
