In the UK you will normally encounter 2 species of cockroach:
The German Cockroach (Blatella germanica): Easily identifiable by the two dark stripes on their thorax. They prefer warm and humid conditions and these insects breed at an alarming rate. The female carries her young in an egg sac under her body until it’s time for them to hatch.
The Oriental Cockroach (Blatta orientalis): Slightly larger than the German at approx. 25-30mm in length and are dark brown to black in colour. These are nocturnal so will prefer to favour dark and damp places so will be prevalent in sewers, drains, cellars, and the like.
The main issues that are associated with cockroaches is the diseases that they are known to carry that can cause serious illnesses including Salmonella, Gastroenteritis and even Tuberculosis this can be a major issue to Hospitals, business, food environments and of course your home.