Looking at it clearly, it is easy to see that it is a lizard, not a snake. Its head is lizard shaped, and although it moves like a snake, it does so because any creature with no legs and a long body has to move that way. It flickers its tongue, but so do most lizards. Despite their name, they can move quite fast, and can disappear into a hole or under rocks pretty rapidly.
We usually find common lizards in the garden at some time during the year, but not very many. We are not only fairly far North, but also our area is quite high above sea level, so we do not have as many as one would find around the Baie de Mont St Michel locally, and certainly not the numbers of individuals and different speciies that are common further south. The other reptile that we have is the salamander, and there is more about that here.
I also saw a quite large lizard, about 8 inches/22cm on a path by the sea on Morbiham, Brittany, a few weeks ago, but is scampered off into the undergrowth. It emerged a few minutes later, but imposible to get near. This photo is an enlarged detail, and not very good, but the best I could do. I do not know what species it is.
(There are related posts here and here.)