"I don't think anyone runs the risk of dying whilst donating semen, blood, breast milk, bone marrow or eggs."
You can catch nasty infections while donating blood, which can possibly be fatal.
And you might like to look into the very serious risks of bone marrow donation.
"The UK, quite rightly, assumes there is a huge problem ethically in paying any of the donors."
But there doesn't seem to be any problem paying surrogates over 10K for expenses".
"So far as the difference ethically between paying for the temporary use of a womb or a vagina- not a great deal -and neither seem particularly desirable."
I agree - ethically there is no difference. There seems to be a moral difference (possibly because making babies even for strangers is good and moral whereas sex especially with strangers is immoral?).
As for 'particularly desirable': There are people, including one on this thread, who say they wanted to be a surrogate and are happy they did it. There are also prostitutes who say they wanted to be one and were happy to do it. Imho it boils down to bodily autonomy - it's her body and she should be able to do whatever she likes with it, including allowing its use by others for money.