Gary,

You're pretty close with Nephrotoma appendiculata, but that species has a pale wing stigma, a darker abdomen (with a mor-or-less continuous black stripe lengthwise along the top) and a much darker head. What you've got here is Nephrotoma flavipalpis, a less common species but one that is widespread across many parts of lowland England. The time of year fits better for flavipalpis as well, appendiculata flies earlier in May/early June. Both species have a black 'inverted-U' mark on the side of the thorax.