Very small hoverfly, much smaller and more slender than the other orangey ones I saw today.
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Thanks so much for the speedy ID.
The only British hoverfly to have pairs of dark bands across the abdomen (a thick band with a thinner, often moustache-shaped, one below). Immediately distinctive for that. If you are into such things, people call it the Marmalade Hoverfly.
My Flickr photos...
Lat/Lng: 51.7, -2.8
OS grid ref: SO4510