The first time I fished Willesley I did about 20hrs in a bitterly cold NE wind in early March.I had 2 fish.We then fished it about another 10 times during spring, summer, autumn and winter but couldnt get on the lions share of the fish during the spring and summer which were in the shallows(field and woods pegs).I wouldnt class it as a hard water at all but in winter I would expect you'd blank more than you'd catch.It seems this is the case as well from talking to lads who have fished it hard in winter.
Incidentally I wouldnt class it as a shallow water the upper part of the lake must account for 50% of the surface area and its over 8ft deep from memory in most places up there apart from the margins and the top bay.If I was looking for a shallow water for the winter I would be looking at somewhere with no more depth than 6ft, above this from my experience the fish take much longer to respond to any good sunshine.
Try Willesley for the winter but I know not many fish come off