There at 2 types of Rat in the UK. The Common or Brown Rat (Rattus norvegicus) and The Ship or Black Rat (Rattus rattus) which is now quite rare.
The Brown Rat is the most common and is the one that you are most likely to encounter in and around your premises scavenging for food and shelter.
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. It is neophobic having a fear of new objects.
The Brown Rat is a burrowing species and is a relatively poor climber. However, it can and will climb when the need arises. It largely lives outdoors but will find it’s way indoors through drain defects, gaps and holes in walls, gaps beneath doors and even climbing rough walls behind drainpipes.