A bit of a puzzle

Not the identification; eventually I managed to work out that it's a Small Magpie Moth (Eurrhypara hortulata).
I had no blip until I came home after work, went to pull down the blind, and there it was, sitting on the window (the flash disturbed it [sorry, moth] and it flew to the wall).
The puzzle is what it is doing out and about in January. They are common in the south of England, less so here. They do migrate in winter (but crossing the Channel to Europe from southern Britain) and mostly they fly in June and July.

The only possibility is that we may have brought a caterpillar or pupa in on some mint from the allotment (the usually feed on nettles, sometimes woundwort and sometimes mint), apparently the caterpillars overwinter in a curled up leaf and hatch in early summer.
Still, it's been a while since we brought any fresh mint into the house....
At about an inch (25 mm) across, these are classified as one of the largest British micro-moths.
I don't care how it's classified, I think he's very handsome with his purple eyes and antennae and his smart black and white wings (view embiggenated!)

Sorry if yesterday's blip disappointed those who imagined me triumphantly plucking tiny ossicles from the soil and bursting into song...here's what a typical day of archaeology is REALLY like (from about 2 minutes in, I think ;)

Off to bed, blipchums, see you tomorrow...