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.
Llangefni
Llangefni is the county town of Anglesey in Wales and consists of the primary offices of the Isle of Anglesey County Council. United Kingdom Census 2011 recorded Llangefni's population as 5,116 individuals, making it the 2nd biggest settlement on the island. The community is near the centre of Anglesey, and is on the River Cefni, after which it is called. Its tourist attractions consist of the Oriel Ynys Môn gallery, which details the background of Anglesey as well as houses the heritage collection of Charles Tunnicliffe. In the west of the community is a huge secondary school, Ysgol Gyfun Llangefni (Llangefni Comprehensive School), as well as in the north a Victorian parish church, St Cyngar's, set in a woody riverside location called the Dingle. The community was formerly called Llangyngar, Welsh for "St Cyngar's church".