What is this insect?

[motco]

It is between 1 and 2mm long and hundreds of them crawled inside my video door bell and they're in picture frames in the house too.

[motco]

essayer said:

Thrips! bd things, get everywhere.

Don't they just! A bit of Googling reveals that there's >170 different ones in UK and 6,000 worldwide. Apparently they are "harmless" but they might "prick". Sodding things! What possible purpose do they serve except to annoy?