I must admit on seeing it for real it didn't look quite the ticket with the labellum being more rounded then what I remember from the Narrow-lipped I saw in the Chilterns a few years ago. Also both perianth segments were also more rounded then long, although it appeared more Violet like then Broad-leaved, but online experts are happy with B-l Hell. Also nearby was a single Green-flowered Helleborine which was roughly 10cm tall, so presumably these are having a poor year locally.
Afterwards a trip to the Downslink produced a single Brown Hairstreak.
This evening a short seawatch down Splash Point produced the following:
Balearic/Manx Shearwater - 1 E at 6.30pm - too distant to be sure but it felt more Balearic like.
Sandwich Tern - 1
Gannet - ca. 25
Brown Hairstreak along Downslink north of Henfield
Broad-leaved Helleborine - so much variation in this species doesn't make things any easier