im following and reading this thread with much intrest as how different people live is very much a intrest of mine,and i could help but do this so sorry in advance.
lots of you are making huge incorrect assumptions about certain systems and households in the uk and its going both ways. we have people in receipt of benefits missing them out with regard to total income,we have people whose salerys to the people on benefits seam huge but then pointing out certan costs but also failing to mention that on the salery stated they should be getting more help.
we also have massive missunderstanding of who should get what sort of help.
fyi.
any family who gets wtc even if its only £1 a week will not under any circumstances qualify for free school meals wtc automaticly exempts you from qualifying no matter what your income. even if it is 10k below the max earnings.no matter what other benefits you recive.
also familys on quite a few of the apparently automaticly qualifying benefits will also be exempt if there total income is higher than a certain ammount no matter how many kids they have.
any family with less than 2 children on a low income will not be getting anywhere near 40k in total income unless they live in private rented in a very expensive area and/or have a higher disregarded income due to a disabled family member.however this is perfectly likly with more than 4 kids and possible with 3 or 4.
a family who jointly earn 40k a year with 2 kids and childcare costs should be getting the childcare element of tax credits at approx 4k a year.(in the current tax year and based on £300pw costs if costs are higher the element will also be)
every child in the uk gets free perscriptions, adults in wales also do.being on a low income in england does not automaticly qualify you for free perscriptions as an adult.
no matter what your income if you do not qualify for exemption from perscription charges if the cost of your perscription charges is a consideration i.e you have a fair few you can buy a exemption cert.
water capping is not automatic for familys on benefits even if you are on out of work benefits.most water boards require you to have more than a certain amount of children under 18 and in full time education(usually 3) if you are on a low income but dont have enough children you can only claim this if a member of your houshold has a disability that requires them them to use more water,they HAVE to be formaly considered to be disabled AND have medical evidence that the disability requires higher water use,or have a condition that requires a large number of home based dressings or on dialisis (any household meeting the last condition can apply) the water cap is approx £450 dependant on what waterboard you use i dont think any board has a cap below £400 at the moment.
housing benefit for working families rarely means full rent paid if you are not a large family. even if your circumstances mean you do get either full hb or mostly hb this does not mean you will get full council tax benefit.
any family even if your mega rich if you are a single person you will get the single person discount from ct.
if anybody within reason 
wishes to just put it out there i am more than happy to work out what you should qualify for using a proper benefits calc not one that wont take into acc the impact of one benefit on another (like the direct gov one does its shite)