Further update
Second session was much better. Not much flow, but used a small cane stick & fished rod-tip to 3 rod lengths out. Was fishing a new stretch - had to cut 2 swims - no one ever fishes this bit.
First swim - on a corner, overhanging tree, happy with the trot - tried various depths - nothing.
Second swim – straight – one small weed bed (didn't fancy this much really) - missed bite first cast, third trot down float disappears - something large sets of downstream. Gave it as much stick as the 2.6 hook length would stand, turned it round – saw a flash under the surface & thought – definite barbel. After some t then turned for the near bank 10 yards downstream so ran toward it – no real access – 6 foot reeds, but managed to get the net with 2 metre handle through & by some miracle, the fish went in first go. Pulling the net back revealed – a big (for me) bream of 5.25lb!
It may not be a great fish by most standards but I was bloody chuffed – and on a stick!