Cheers, Wurzel!
I've noticed from watching Holly Blues slurping down on the brambles that the leaves are covered in honeydew at the moment, and it is therefore possible that the male Brown Hairstreaks are behaving more typically this year and actually staying in the trees as there is no need for them to descend into our world to nectar.
Tuesday 30th July was forecast to be a hot one, and the Met Office were spot on: it reached 32 degrees and the sun shone for 13 hours locally. I did a local walk in the relative cool of the morning, and the first butterfly I spotted was a Speckled Wood behaving in animated fashion on the ground and in the shade. It turned out to be a male which had found a female - which was playing dead as they do when rebuffing a suitor.
The male soon gave up.
Further on, I decided to investigate a separate meadow which had not been cut by the Heathrow mowers. I'd been recently told by the folk that look after the whole area on behalf of LHR from a conservation perspective that it was not "out-of-bounds", so it was definitely worth a look. What spurred me into action on the day was finding a Brown Argus just outside the gate to the field and seeing Common Blues just on the other side. I hopped (OK, clambered laboriously...

over the gate and found a very overgrown meadow, but along its northern edge was a thick bramble hedge, and below that the grass was shorter and lots of trefoil and other flowers had been able to force their way through. I wandered the length of this hedge, disturbing both Brown Argus and Common Blues all the way along.
I couldn't help noticing that the spot was precisely in line with Heathrow's northern runway, and with the easterly breeze planes were coming into land immediately above me - no more than 50 metres up. The butterflies seemed unaffected by this distraction, though there were some unusual wind effects from time to time. In fact, I spotted a mating pair of Common Blues, which posed nicely for some time.
A bit of context...
A few more (unattached) Common Blues...
...and one of the Brown Argus.
The latter species were very active in the sunshine, chasing each other and disturbing the Blues as well.
I found a few more Common Blues along the midline of the path on my walk back. This also didn't get mown and has sprouted trefoil in many places along its length, and is an instant attraction to both sexes of the species when the sun shines.
Overall today before it became really too uncomfortable to keep walking, I counted 169 butterflies of 14 species - here are some of them...
Curiously, I didn't see any Holly Blues today, despite the availability of shaded bits of damp path...
Dave