The common wall lizard (Podarcis muralis) is a species of lizard with a wide distribution in Europe. Although it probably wasn't native to the U.K., it has been introduced there in modern times with now several growing populations present in different parts of the country. It has also been introduced to North America where it is sometimes referred to as the "European wall lizard". It can grow to about 20 cm in length, and is a small, thin lizard whose scales vary greatly in color and patterns, as you can see in the photos below. Common wall lizards mainly prey on insects, spiders, snails or worms, but they aren't picky and eat pretty much any creature that is small enough to fit in their mouth (and also the occasional berry).
Podarcis muralis often share the same habitat with the much larger western green lizards (Lacerta bilineata), and in case you were wondering how they get along with their bigger cousins, the answer is: it's complicated.
Smaller individuals of Podarcis muralis run like hell if they happen to get close to a fully grown western green lizard (because they rightly fear they might get eaten), and even the bigger common wall lizards seem to at least avoid their green neighbors. But it's not uncommon at all to see the commons bask in the sun right next to the bilineatas or even climb over them without any signs of fear. So it might depend on the specific habitat they share, how abundant food is for both species and if it's even possible for them to avoid each other. Common wall lizards do occasionally prey on each other (I witnessed one such incident and filmed it; there's also a photo of the "cannibal" below).
What's fascinating also is that Podarcis muralis occur in at least six different morphs, which is not all that common among the same species, let alone within the same habitat. So if you've ever observed dark green individuals with orange bellies and brown ones with nearly white undersides and grey ones that are ornamented with blue "sapphires" on their sides, and you came to the conclusion that those must be the differences between subadults, males and females, the correct answer is in all likelihood: nope.
They may all well be around the same age and of the same sex and definitely of the same species: it's just that these lizards apparently have evolved into six different "looks" (which also come with certain other distinctions regarding for example their immune systems; you can read about all that on Wikipedia). In addition to that, there's also regional differences, so I guess it's fair to say that common wall lizards don't like to be all that common and have a knack for colorful variations :-)
All the individuals below I photographed in my garden in the Ticino (Switzerland) or its immediate surroundings.