Confidence: I'm as sure as I can be.
Notes: Were found (&plucked from) rim of a shoe (so true stalk lengths) .
of the 4 (or 5) Lepas species found on uk beaches only 2 have the like furrowed surfaces (according to species.org); this & L. ansifer.see the species.org sites below for the illustrations & descriptions used here.
For Lepas pectinata see
for Lepas ansifera see
It fits all the L.pectinata characteristics described there as (apposed to L.a.) . Narrow peduncle (=stalk); length of capitulum (=shelly bit) (to15mm for L.p & to 40 mm for L.a). Scutum ("main plate") tends to triangular (more quadrangular in L.a). Tergum ("lesser plate") almost triangular.