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.
Menai Bridge
Menai Bridge is a village and area on the Isle of Anglesey in north-west Wales. It forgets the Menai Strait and lies by the Menai Suspension Bridge, constructed in 1826 by Thomas Telford, just over the water from Bangor. With a population of 3,376, it is the fifth biggest community on the island. There are lots of small islands near the community, consisting of Church Island. The Menai Heritage Bridges Event celebrates the world-famous Menai Suspension Bridge, built by Thomas Telford, and also the Britannia Bridge, developed by Robert Stephenson.