It is unfortunate that he suggested shaving the NHS budget because that is what everybody will pick-up on - as demonstrated by the question.
However, there are plenty of other areas where money could be obtained from. The overseas aid budget is an obvious choice - China, India and Brazil, all of who receive our aid, but don't really need it. I accept its a quid pro quo thing (we'll give you money - you buy our products), but there has to come a point where we stop giving 'aid' to countries which have a larger economy than ours.
Another area is benefits. We have a large number of people doing nothing, have never done anything, and have no intention of ever doing anything, but receive generous benefits because.....wait for it......"I'm entitled to them". This feeling of entitlement needs to stop, and the obvious way to stop it is to stop paying them so they have to pay their own way. This will be good for them and good for society. People choosing to do nothing, when they are perfectly capable of doing something are stealing from the taxpayer.
Frontline services should be ring-fenced. I hear the term 'front-line services' a lot, which presumably means there are second, third, fourth etc... line services.
Scrutinise the tertiary services to see whether they actually deliver anything worthwhile.
It is ridiculous that our Navy has shrunk to this degree - and our lack of carriers is a national embarrassment.