Power Sport in Bradford were stockists when I bought mine a few years ago. Thunderchild are the importers for Roof so may give you more up to date info, Have found mine to be a decent helmet barring iffy top vents, think they have improved the plastic as second free replacements have lasted the course.
Don't do it, you're struggling to find one coz they are hard to get hold of, I worked for a roof dealer for 3 years and had nothing but trouble the hole time, mainly due to the fire at the factory but it has taken far too long for them to recover and quality is a best poor. Thunderchild are the UK importers and a right waste of space they are. I reckomend Shoei or schuburth the only two manufacturers to have a wind tunnel.
cheers folks went to eddy wrights in leeds he sells the full range /didnt pur chase as they dont fit my heed shame as there a smart looking lid ,,, think ill have a look at the flip up cabbage lids instead ,