This is pretty shoddy reporting

UK museums hold more than 263,000 items of human remains from around the world, including whole skeletons, preserved bodies, such as Egyptian mummies, skulls, bones, skin, teeth, nails, scalps and hair.

So, to be clear, they aren't distinguishing between an entire mummy and a lock of hair.

37,000 items of human remains are known to originate from overseas

Experts said the findings contradict a claim made by the Department for Culture, Media and Sport (DCMS) in its 2005 guidance that said “the vast majority of human remains in UK museums are of UK origin

37,000 / 263,000 ≈ 0.14 or 14%. Am I wrong to think that 86% qualifies as a "vast majority"?

Honestly the stuff the British stole in the colonial era just really stinks. Its shameful.

Even when they didn't colonise a place, they showed up and introduced syphilis and small pox and stole some cultural relics and were just generally huge assholes.

Just repatriate all of it. Every last arrowhead.