1200 dpi scan
No interactions present.
Could be an old mine of Aulagromyza cornigera. This is supposed to occur earlier in the year, but the cold weather in May could have held things back. The frass pattern could pass for cornigera - hendeliana is said to have 2 neat rows of frass. Have you run the mine through the Dutch site key?
Dutch key says that A. hendeliana has frass in discrete granules, which fits.
University of Edinburgh and Biodiversity Observatory (OU)
Lat/Lng: 52.0, -0.7
OS grid ref: SP8936