I was getting very cold feet on long rides so was advised to go for a set of overshoes. I went for these and they definitely did the trick.
However, and this is why they only get 2 stars, they already have a large hole wore into them at the heel after 1 ride! After further investigation it appears that they are too loose around the ankles and they slip down over the heels. This has subsequently caused the hole to appear after walking only a short distance into a cafe for a brew.
Therefore, I would only get these if you have massive ankles or some way of stopping them slip down!