Found reviews of thrm as Kabuto MS-2, apparently designed in Japan then made in Singapore. No mention of CE markings or testing to EN whatever so they might not be intended for UK sale.
I'd say use a retailer you trust and know will have legit stock, fake helmets are a thing now.
Anyone ever use a OGK? I want to spend less than a 100 quid and these seem really unique.
http://www.alexscycle.com/helmets/ogk-1/ogk-kabto-sword-bicycle-helmet-ms-2.html