Confidence: I'm as sure as I can be.
Notes: I'm saying I'm as sure as I can be based on the fact that speckling is visible "anterior to the radial vein" on this caddis. The Adult Trichoptera of Britain and Ireland by Barnard and Ross(2012) differentiates between S. permistus and S. vibex by the presence of speckling forward of the radial vein- vibex hasnt got any but this caddis does. The pale dorsal stripe is a key feature of both Stenophylax species. This doesn't appear to be the similar but more compact and generally smaller Micropterna sequax, its a much better match for Stenophylax.