Everything has a risk element attached to it. Of course there's a risk of dying with nearly everything we do nowadays. Bear in mind, it's highly occasional that you will end up dying however the risk is still there. The stories that come up in the papers about a trial like this going wrong only happen once in a blue moon since they don't highlight every single successful trial. £5,000 is a lot of money. Personally, I would do it but since it's your body and your decision, you should have the final say.