A little small than a hoverfly. The all green one was smaller than the green / blue one.
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To say 'a little smaller than a hoverfly' does not mean a lot. A big Sericomyia silentis or Volucella pellucens may be 15mm long, but other species never get longer than 5mm!
I can't help with the ID of these flies, though.
recording wildlife with The Recorder's Year on www.hbrg.org.uk/TRY.html.
I would say that the green / blue one was about 2/3 the size of [say] Eristralis Tenax.
Lat/Lng: 50.72065, -1.84701
OS grid ref: SZ108912