> And therefore are also very likely to be descendants of those people to some (possibly non insignificant extent) extent.
We (the UK) don't care. If you try to export human remains from the UK to another country (the study is being done by US and Australian universities), without the correct permissions you're going to have a bad time.
If it is bad for the British to take human remains from other countries, then we should apply the same logic to exporting British human remains.