though the tendency of health spending to always grow faster than inflation means there will be areas of cuts there too, to make up for other areas. And the coalition government has a plan to reorganise who controls the budgets (they want consortia of general practitioners to do it, rather than the local appointed boards that do it now) which may end up costing more money, so that may hurt spending on actual health too.
That BBC page is as good a summary of the whole process as you're likely to get. I have the feeling the 40% figure was meant to scare people into accepting 25% cuts as 'OK'. But 25% is still huge, and many economists say there's a high risk of going back into recession if these cuts happen, because - including, ironically, some government bond investment companies, even though the government claims this has to be done because the bond investors demand an immediately cut in government borrowing.
Accidentally (or not, you can never tell), the Treasury Chief Secretary left some pages photographable today, which say the govt expects half a million public sector jobs will be lost because of the cuts:
http://www.guardian.co.uk/politics/2010/oct/19/spending-review-document-job-cuts . That's another 1.6% on the unemployment rate.