War Peaceman
You're a big guy.
This is as good a breakdown as I could find on what proportion of the benefits (and tax credits) bill is taken by each sector of the population. This is based on 2011-2012, so I'm sure the numbers will look a little different today. There is a lot of information here that is unknown by the proverbial man in the street.
http://www.ifs.org.uk/bns/bn13.pdf
Families with children: 18.41%
Unemployed people: 2.67%
People on low incomes: 20.8%
Elderly people: 42.3%
Sick and disabled: 15.53%
Bereaved people: 0.31%
Looking at individual benefits as opposed to the people who receive them, we see the "big beasts" are as follows:
Basic State Pension: 28.88%
Housing Benefit: 11.31%
Child Tax Credit: 10.96%
Additional State Pension: 8.02%
Disability Living Allowance: 6.26%
Child Benefit: 6.08%
Since there's been a continued effort to move people off DLA and on to the Personal Independence Payment, which has significantly more stringent criteria, I would assume that the government spends less on it today than it did in 2011-2012.
You will note, of course, that a family with children could contain people on low incomes, in which case they could draw benefits from both groups (e.g. Child Benefit + Child Tax Credit + Housing Benefit, possibly Working Tax Credits or Council Tax Benefit too).
There's a simple and depressing explanation for this. Old people vote.