At first I thought this tiny insect flapping through the garden was some sort of moth. When it tarried a short while on the lavender, it became clear that it was a small skipper butterfly.
The lavender flower gives an idea of size, less than 2cm long. These butterflies mostly appear in UK at the height of summer, mid-June to mid-August.
This photo from a previous post shows the small skipper on thistle flower, with wings extended.
And here’s one on buddleia in typical half-open pose.