I agree about the grey population spending less as it grows older. From a demographic point of view the UK may not be the best place to invest since the boost in GDP growth from the baby boomers in the 80s and 90s has eased off, as has the impact of increasing numbers of women entering the workforce. According to Jeremy Grantham's take on US population growth and GDP on the GMO website, the Western World may not be the greatest place to be investing for the future.
I agree that health will be a big issue so WWH Worldwide Health IT is a possibility. Biotechnology has outperformed in recent years eg Biotech Growth BIOG so will that continue? GP property has always been a safe and effective investment for GPs, with guaranteed Government reimbursement for NHS use of premises. Now there are Primare Care Property funds like the already mentioned PHP and there's Medicx Fund IT currently at a premium of +22, with a dividend of around 7.5%. Whether this will always be a guaranteed safe income stream seems likely but bear in mind no one seems to know where primary care is going at present.
If you can get over the fact that PFI contracts have been badly written and sometimes rip off the NHS etc, then HICL, JLIF, INPP, GPC infrastructure etc. appear to provide a relatively safe income stream with some capital appreciation though all are running at a premium. I've seen a feeling expressed that it would be easier to let an NHS built hospital go to the wall than a PFI one if the market becomes more competitive and if hospitals fail.