Confidence: I'm as sure as I can be.
Notes: We need to be careful about what is going on here. The ID offered was Lema sp., but that has been transformed in the links below into L. lilii. I think we can be certain it is not L. lilii, and NBN does not recognise any genus Lema for UK. A coleopterist is what we need. Meantime I am making it the Order just to maintain accuracy (if not precision).