If I absolutely know that I am safe, but the policy does not allow me to donate, then I would have no problem lying to save a life.

If I (and this is taking extra-wide margins) have not had any sexual contact in the past 12 months (or anything else that leads to something like HIV, such as needle use), and have always tested positive, then any doctor would confirm that, as long as I am telling the truth about this situation, I am definitely clean. And yet I would still be banned from donation. Do you really think that, in that scenario, it would be wrong to lie if I could specifically save somebody's life?

A lifetime ban is quite clearly over the top and not neccesary - hell, even with the UK's new 12 month waiting period after MSM activities for donating blood, there is scope for someone to have gone far past the window of "I might have HIV from that person and it isnt showing up yet", without having reached the 12 months required by policy.

I absolutely would not endorse lying in this situation, apart from anything it is possible to be 100% confident that you are safe and clean, and be mistaken. But in a certain scenario, I would be willing to lie personally.