Right - I'll have a stab...
I reckon there is a HBF lurking there amongst all the DGF, but I don't think it's the last one. The butterfly that immediately made me think High Brown was in the first set of three, the one annoyingly half hidden by grass on the bottom right. I suppose you'd like me to say why as well...
All the butterflies are males as far as I can see, which doesn't help. Both species do have sex brands in the form of slightly broadened forewing veins (nothing like those on SWF, though). However, though these are barely discernable on DGF and gradually widen and narrow again, on a male HBF the second two veins have a noticeably broadened section which appears more abruptly.
Here are two close ups which hopefully show you what I'm on about:

- DGF - gradual and narrower

- HBF - abrupt and wider
(the DGF is from Box Hill, and the HBF from Arnside last year - I have an underside shot of the butterfly to prove it!)
Here are close ups of the relevant bits of the last butterfly you posted (which I think is a DGF), and of the one I think is a HBF.

- DGF veins2.JPG (50.97 KiB) Viewed 195 times

- HBF veins2.png (62.43 KiB) Viewed 195 times
They seem to match. All the rest look like DGF.
What do you think?
Cheers,
Dave