I came across this grousing article about picnics and thought I'd share it.
To add my two cents, I will say that Iceland has even more notoriously fickle weather than Britain and I have still managed to have some perfectly lovely picnics here.
Simple picnics with sandwiches and cakes and tea are lovely when the food is done right and the weather behaves, but the picnic meals where we cooked the food on the spot were always my favourite, especially the ones combined with a day at the beach: wading in the sea, collecting shells and semi-precious stones (jasper and chalcedony), and gathering driftwood, dry seaweed and garbage that had accumulated on the beach since last year's outing and piling it up to make a bonfire.
This would be followed by charcoal-grilled sausages in charred buns or lamb cutlets and baked potatoes with salad, and drinks cooled in the river, followed by a lazy hour or two in the sun, digesting the food and talking, and then, when it began to get dark, lighting the bonfire, listening to the driftwood crackle and watching the flames leap. Then home, slather on after-sun cream and to bed and a deep, restful sleep.
These picnics were always spontaneous because we could never rely on the weather forecast, but it only added to the fun and I don't ever remember one getting disrupted by bad weather. Nor do I remember wasps in the food, but there must have been the occasional midge.