There are 2 main species of cockroach that have made themselves at home in the UK: the Oriental cockroach and the German cockroach (not actually from Germany). The adult Oriental cockroach is brown and 15-20mm long, and the adult German cockroach is dark brown and 10mm long.
Treating an infestation of German cockroaches is relatively straightforward once we find where they are hiding! They tend not to stray far from their nest sites and can usually be eradicated along with their eggs. After an initial survey and treatment at least one follow up visit is recommended and depending on the scale of the infestation, that may be enough.
With an infestation of Oriental cockroaches the treatment is often slightly more complicated. This species travel further from their nest sites so can be harder to track down, they also have an annoying habit of leaving eggs concealed which can then hatch after a few months and give rise to a second infestation. So if the initial survey detects Oriental cockroaches the initial treatment must be followed up with monitoring program for a few months after to ensure they are completely eradicated.