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I had greed the species but I really am not sure, just had a look in Waring, I had originally agreed on crossline shape but not confident. The lines do look right for your suggested species.
I've never seen a Canary Thorn as 'clean' as this one. I think they always show a degree of speckling and blotchiness with more prominent venation and the thorax is always distinctly yellow. But the clincher is that the cross lines should meet the dorsum at an acute angle on Canary not at 90 degrees as in the photo. It's definitely a September.
Lat/Lng: 51.2, 0.1
OS grid ref: TQ4849