The House Mouse (Mus domesticus) is common in a variety of urban and rural buildings throughout the UK.
It is omnivorous eating more or less any food available which is why it is quite at home in an urban environment as well as rural locations. Unlike Rats, mice do not need to be a near a water supply as they can usually survive on the moisture they get from their food.
The House mouse is a very good climber and can even scale vertical walls if the surface is sufficiently rough. Gains access indoors through small gaps and holes in walls, gaps beneath doors etc.