Realistically, the "cost" has to be shared over everyone. Every tax needs to rise by a small amount, so say an extra 1% on income tax and corporation tax, 1% on VAT, 1% on fuel duty, insurance premium tax, tobacco and alcohol. At the same time, benefits need to be held back slightly, so instead of, say a 2.5% inflationary rise, scale it back by 1% to just 1.5%.
Then remove some of the exemptions/reliefs on inheritance tax and capital gains tax.
Big tax rises for any particular demographic will have adverse unforeseen consequences - we really don't want to end up with less tax revenue by making an ill-informed tax rise, such as when Gordon Brown brought in the 50% top rate of income tax that caused an overall reduced tax take from those in that bracket!