That £5Bn pa (in the ten year production phase only, thereafter £1.5Bn pa), represents less than 4% of the annual NHS budget - or two weeks running if you want to put it that way.
Point on pensions is well made - but I suspect that comes out of the £250Bn welfare pot, not NHS running budget - although happy to be corrected.
Point being we cannot keep funding what is in effect an unconstrained demand for "goodies" (pensions, healthcare, degree education for all) - particularly not on the backs of 5% of the population. There is a complete reluctance to address this - immediately accompanied by platitudes about "our NHS", "rights to free higher education etc".
People are living much longer, more complex (and expensive) treatments are available, population is increasing etc etc and yet any attempt to make anyone other than "the rich" pay for this is treated as an outrage, let alone questioning whether fully tax-funded is the right model any more. The French and German healthcare systems usually quoted as the exemplars of what the NHS aspire to are rarely noted as having a significant chunk of personal contributions.