Most of these will be Queen wasps looking for suitable places to start building her nest.
The Queens mated last year and have hibernated over the winter period and now emerge as the temperature warms up.
The rest of last years colony have died. Wasps are considered pests by many people but wasps help the gardener by eating caterpillars and aphids.
The large yellow and black insects flying about are not only Queen wasps though, there are also Hornets.