Neil, I can recommend the free stretch at Runnymede, just west of Staines- come off the M25at J13 and take the A308 for 1/2 miletowards Old Windsor, that's the opposite direction to Staines town - and there is a council car park with a cafe on your right. Turn left as you go in and drive parallel to the main road up to thefar end of the car park and you're right by the river.
There are ticket machines nearby for parking but it's best tohave a quick look at the river before paying - you might not fancy it and then youwon't have wasted your money!
Where the car park meets the river it's about 15' deep on the bend and it can tow hard when there's a bit of water on. The depth drops away as you go downstream so pick your spot to suit the water conditions - about 150 yards downstream you have about 8' a couple of rod-lengths out. There are bream along the deep bend, also good roach and perch. In warmer conditions you can get pestered by small roach, dace, bleak, but in winter you will mainly get quality fish. I have heard of big chub to maggot feeder fished across to the trees but have never tried this. Mainly you will need stick float gear, preferably a longish rod (I use a 20') or a pole. You can also pick up nice fish on the bomb or small feeder quite close in, as the margins arequite deep.
We generally take bronze maggot with a few reds, plus casterand hemp - it's a good idea to feed using a dropper to start with so you get a bit of bait on the deck. Then just keep feedinguntil something happens! I have seen 30lb+ bags of roach here in the right conditions, ie. fining down after a flood, with everyone on the stretch catching on a variety of baits and methods.There are some cracking perch here, too, and the downside is there are some nuisance pike, too - but that just shows how many fish there are here!
All in all I'd rather have a hard day here than an easy day on some overstocked carp puddle wherea monkey could catch 100lb!
Good luck!