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That looks like a solitary wasp, and an ichneumonid, but I can't work out which one. None of these quite seem to fit, perhaps the closest is amblyteles armatorius (but as the guide isn't complete, it may not be in there):
https://www.naturespot.org.uk/sites/default/files/downloads/british-ichneumonid-wasps-id-guide.pdf
Shame you didn't get a picture of the hornet. Hornets and wasps are much less aggressive close to their nests than honeybees, by the way.
Stopped while out riding at the weekend and leant my bike against a log pile. The biggest hornet I have ever seen buzzed out and landed on my tire. I couldn't get a pic quick enough before it buzzed back into the pile. There was also this one that was frantically rubbing its abdomen against a log for some reason.
Very wary of being that close to a potential hornet nest so made a quick exit.