Ant invasion...

You will have numerous ants nests under the paving - just the sort of area they love. Any pots stood on paved areas should be on pot feet, or raised off the ground slightly with bits of broken roof slate, anything that keeps them off the paving. You can also, when you repot, use half a jeycloth (or weed suppressing membrane) in the bottom of the pot to help keep them out.
In the meantime, buy a pesticide spray which treats for aphids and use that on the plants, but don't spray any open flowers, and spray in the evenings when the bees have stopped working. If you think you might have a nest inside the pots, turn the plant out and check - ants don't eat plants, nor their roots, but if they decide to make a nest inside a pot, they will chew through roots to make more room for their tunnels. Soak any plants which do have ants nests inside in a bucket of water to get rid of the ants, then repot in fresh compost.

Or you can reduce the number of ants under the paving by pouring kettlefuls of boiling water over them and into the nests. It won't get rid of all of them but you can reduce the numbers to levels that don't bother you. Just repeat as and when necessary to knock them back to unnoticeable levels.