Although many of us regard squirrels as a beautiful a part of urban life, they’ll be a nuisance after they cause injury in gardens.
More serious issues could also be experienced once squirrels:
find their approach into lofts and roof voids wherever quite excluding the disturbance caused by their nocturnal activities
gnaw structural timber
foul insulation material
gnaw of electrical cables
If the primary drawback experienced is one among noises within the loft and if no squirrels are seen then the noise might presumably result to birds, rats or mice.
An examination of the loft to seem for proof like faecal matter or nesting material could facilitate to see the reason for the noise.