i have heard that feeder fishing hemp/maggot is good on the hants avon, if that dont work try the usual running leger with meat, corn, worm, paste, boilie, pellet etc on the hook, fished over a bed of hemp or pellets, corn, particle mixes ( wheat, groats etc )
i havent seen the hants avon before but if runs with streamer weed/gravel bottoms and good current are about try rolling meat or campbells meatballs, cast it out and let out some line and let it roll through the swim in a natural way ( a straight line, not letting it pull back round in an arc ), you should be able to feel as a fish picks up the bait.
this is only general advice i have never fished the hants avon myself, i spend most of my time blanking on the gt ouse, obviously asking someone who actually fishes the river would get you a better idea but i hope that helps anyway
cheers Daniel