Strange fly, on quiche packet.
No interactions present.
I agree that it is a parasitic wasp, probably in family Ichneumonidae, but don't know them well enough to say any more than that.
Entomologist and biological recorder
Dear Martin, yes, in our book on insects[Michael Chinery] there are some other possibilities but this seems the most likely.
Chinery is a fantastic book and one of the best ways to get started with insects, but inevitably it can only illustrate a small proportion of the total number of UK species, and with ichneumons there are hundreds of species that aren't in Chinery - one reason why I've never managed to make much progress with this group!
You can download a checklist of the British species of Ichneumonidae from the Biological Records Centre, but it runs to 162 pages (just for the list of names, no pictures!). They also provide a (fairly complicated) key to the subfamilies. Both these can be downloaded from:
(scroll to the bottom of the page under the heading "Taxonomy, phylogenetics and phylogeography")
Lat/Lng: 53.343476511975, -1.7609791158975
OS grid ref: SK160829
Edge of river.