It is a busy time of year for us right now with Wasps being a nuisance. Wasps can fly up to 750m from their nest so you may find a lot of activity even if the nest is nowhere near where you are observing them.
Wasps will feed naturally on the sugary liquid secreted by the wasp larvae but this means that they are often very attracted to other sweet substances, e.g. windfall fruit, sugary drinks and spillages.
Its important to keep in mind that when a wasp stings or is killed the venom released is often smelt by other wasps which can in turn become more agitated and potentially aggressive.