Your advert is potentially visible UK-wide. Anyone from anywhere in the UK can see your advert, as long as it falls within the geographical search radius they have set.
Users can search the whole of the UK or just their local area, and determine their own search radius.
The default search radius for local searches on the Friday-Ad website is 20 miles (100 miles in the app). This can be reduced or widened from 0 to 100 miles from any chosen location.