Trichopsocus brincki
The NBN Atlas doesn't show any records of this species in East Anglia but this resource seems to be quite incomplete for Psocoptera. However it is described as scarce at the National Barkfly Recording Scheme website, but given that I've found several I presume it isn't all that rare here.
This is a small species (the detached forewing shown below was 2.25mm long (including the apical cilia). The pterostigma is evenly thick, and darkened, and there is an additional long dark patch nearer the base of the forewing (look carefully - it's not all that obvious). This one was found on pine.
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female Trichopsocus brincki showing wings, Dillington Carr (Norfolk, UK), 29th January 2022
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Trichopsocus brincki showing forewing, North Elmham (Norfolk, UK), 17th September 2016
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Trichopsocus brincki, St Mary's churchyard, North Elmham (Norfolk, UK), 26th February 2022
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2x Trichopsocus brincki, St Mary's churchyard, North Elmham (Norfolk, UK), 26th February 2022 (first two photos are the same individual, third is a different individual)