Deliberately introduced to this country sometime in the 19th century the grey squirrel has since spread throughout most of mainland England and Wales. Mainly a resident of broadleaved and mixed woodlands it is also a common resident of urban parks and gardens.
They frequently enter domestic roof spaces. Once inside they chew woodwork, strip insulation from electrical wiring and water pipes, tear up fibreglass insulation and, occasionally, drown in water tanks.
REMEDY: Physically blocking gaps and entry holes with wire mesh is the best answer. Various types of trap are available as is a poison based on warfarin, but only to professional technicians. Release of grey squirrels caught in cage traps is illegal.