i bought a pair of neoprene chest waders 5mm from nwac(wigan) for ?39.99,i have used them 3-4 times aweek and they are brilliant value for money
they have built in welly with felt sole and i have never felt that i have needed studs,and i have fished on slimey rocks silt bottmoms,etc,and if they only last this winter i will have had my moneys worth(i feel i have now)although i can see them lasting a couple of seasons,
personally i wouldnt go for thigh waders,you always get tempted to go that little bit further,and some of the smallest rivers have deep holes in them as i found out recently while trying to get a chub from round a bend 1 step to the right where i hadnt prodded with the wading stick and the water was over ,
the top of my waders
but being neoprene i didnt get out and dry of,the water inside warmed up like a wet suit
good luck with your choice
paul