In a nutshell – offer teams a 4 day week with the 5th day unpaid, automatic 20% saving on salaries.
The overheads for the buildings and so on are going to have to be paid anyway, so that's a fixed cost. If a large number of people opt for this then they will save the kinds of figures looked for but without tearing the heart out of communities in Scotland and Wales that are very dependent on government jobs.
This is an easy way to cut costs and free people up to be more productive by encouraging them to start small enterprises on their "5th day". In areas of high unemployment it could even be used to create jobs by asking people to pull together.