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.
Llanwrda
Llanwrda is a village as well as neighborhood on the River Towy, in the region of Carmarthenshire in west Wales, situated some 4 miles (6.5 km) southwest of Llandovery. The village is served by Llanwrda train station. The south end of the neighborhood is intersected by the A40 road in between Llandeilo and Llandovery and the village stands at the junction of this road with the A482 to Lampeter and also Aberaeron. The neighborhood is bordered by the communities of: Cynwyl Gaeo; Cilycwm; Llandovery; Myddfai; and Llansadwrn, all remaining in Carmarthenshire.