I'm using a pair of Diawa ones at the moment. I've also used Airflo ones in the past and they've been fine. Keep an eye open for the offers in the Trout mags and aim to pay about ?60 nto ?80. Glasgow Angling Centre and Fish Tec are worth a try.
One tip if you're not going to wade on bouldery bottoms (what a thought!!) is to buy a cheap pair of work or hiking boots and punch a few drainage holes on the instep just above the instep. They're much better than felt soles for walking on grass and mud.
I use mine like a pair of waterproof trousers for genral roving and boat fishing.
I have got the Wychwood Neoprene chest waders, had them about 4 years,
very warm in winter, during the summer i just put on shorts under them never let me down. Patch on the backside and knees for extra wear and tear. I thing they cost around ?70.