You should pull up and remove weeds by hand as and when they appear. If it is a regular problem, you might need to reseal the paving. In extreme cases, the sub layer itself may need to be re-laid. You can use weed killer, however some paving can be discoloured by stronger weed killers.
Grange-over-sands
Grange-over-Sands is a community and civil parish located on the north side of Morecambe Bay in Cumbria, England. Travelling by road, Grange Over Sands is 13.1 miles (21.1 kilometres) to the south of Kendal, 14.9 miles (24.0 km) to the east of Ulverston, 25 miles (40 kilometres) to the east of Barrow-in-Furness as well as 28.1 miles (45.2 kilometres) to the west of Lancaster. Historically part of Lancashire, the town was developed as a city area in 1894. Given that 1974, adhering to city government re-organisation, the community has been administered as part of the South Lakeland area of Cumbria, though it remains part of the Duchy of Lancaster. It had a population of 4,114 at the 2011 Census.