Take some sweetcorn with you, it often works if maggots are proving a bit slow. If you can still fish the 2nd carrier at Timsbury (the fast clear one) then that's always worth an hour or so. Don't be put off by the depth and clarity. Look for a slightly deeper run and there will be some grayling there. Never had an awful lot of success on the main river, but it looks superb. You'll have a lovely day whatever happens.
With regards to end tackle: 16 hook, 3-4lb mainline, slightly weaker hooklink. Smallish float maybe 4 to 6bb. Make sure you try several approaches when running the float through. At first run it through at current speed, mending the line as and when. Then try holding back slightly and even holding back hard, allowing the bait to flutter up high in the water whilst keeping it almost stationary. Keep changing baits and if necessary hook sizes until you get a few bites. Don't change too quick though, try giving each bait a decent chance. Keep a steady trickle of bait going in or even use a bait dropper to get a few maggots down. Rest the swim for 5 minutes and then fish.