I know what you mean, and I know this is Curmudgeon Corner, so not really the place to examine this, but I think a lot of people did the clapping/pot banging thing as it turned into a way to demonstrate the level of support the NHS had. I did it, partly as a gesture for the NHS people in a difficult time, but also as a 'keep your filthy hands off the NHS' gesture. But then I'm prone to pointless gestures like that.
Blood donation, excellent idea, good thought. Given what you drink, is there any way to express a preference for yours, should I ever find myself in need?