Graham,
Sounds like you're somewhere near Stour Provost, West Stour or Fifehead Magdalen; I've fished near the last of these. It's very narrow, surprisingly deep in parts. When I fished it there were lots of chub around 1 - 2 lb plus roach to a pound, good dace and a surprise bream. Not much sign of perch though this may have changed. Caster was best in summer using a stick, or bread punch on little Avon float and 16 hook with a little groundbait in winter when conditions were ideal, tinge of colour slightly up. Very prone to floods in winter, can be 12 ft up. Interesting rather than world beating. Rumour of barbel being stocked in this area but no actual evidence. Odd pockets of big roach to over 2lbs..
Mark