If RPM's still looking in I'll add my two bob's worth - having caught barbel around Newark.
If the river's carrying up to three feet and is coloured with not too much debris coming down you've got good conditions that are easily managed.
Five or six ounces should be enough. If that won't hold try casting upstream and feeding a BIG bow in the line. So much of a bow that the line enters the water downstream of your rod. If that doesn't work seek out a spot where the lead will hold.
A good area type to look for is a crease just below the inside of a bend, with slacker water (or an eddy) close in. Fish your baits on the crease, or slightly further out, towards its downstream end - not in the slacker water. Use the slacker water to keep water pressure off the line.
As for tackle I'd step up the 10lb braid to 15lb mono or 30lb braid for the mainline, and 10lb mono or 20lb braid hooklinks. Set the baitrunner just tight enough to stop the rod getting dragged in. That helps set the hook and keep it in. There's no need for a quivertip for Trent barbel! A running rig and hair rigged pellet is spot on. I prefer a long hooklink - up to five feet, but three is okay - to prevent line bites and instil confidence in the fish.
Keep it simple and you'll do fine.
Hope this helps a bit.