While I cannot comment on your husbands salary, benefits, etc., I can help with whittling down the day to day expenses that you have.
First of all, start a spending diary. Every cent you spend or give to the kids, write it down. DO NOT LEAVE OUT ANYTHING. This is going to help you determine where your money is going, and where you can truly cut back. At the end of each day, look at the days outgoings and be honest with yourself; could I have skipped that today? Did I/they really need that fiver for lunch when they could have made a sandwich at home? etc. etc.
I come from a big household (one of 7 siblings) and so I understand the cost that comes with feeding a big brood. You need to be purchasing good value items that will stretch for you - potatoes, pastas - foods that fill while being relatively kind to the wallet. One of the biggest things to do is obviously to meal plan so there is no waste, and always use up any leftovers. And of course, switch to Aldi's or Lidl's to be kindest of all to your budget. This is where your role as the person at home comes in; you need to take control of this, and ensure your kids and husband take packed lunches with them every day - there should be no eating out costs and no money being handed to the kids to eat out.
Your child aged 18: Its time to get a job. I've worked in part time or summer jobs since I was 14 years of age, and its part of growing up. I contributed each week to the household financially (1/3 of my wage when part time, 100 per week when full time in the summer). I appreciate jobs are harder to come by right now, but they are out there. A friend was offered three part time jobs this week. Your Son (apologies if wrong here, I believe your eldest is male?) needs to do his fair part and its time to reduce the burden at home.
Your child aged 16: The same applies. A fine age to start a part time job if they can, and if not there are odd jobs, babysitting, grass cutting, etc. Get inventive.
I assume the two eldest have mobile phones - and I can see you have a Phone cost of 170 per month. I have to assume that the mobiles are covered under this. Please expand for me if you can, as to the cost of each persons plan, and how you come to this amount - does it include a house phone? If you have your children on Bill phones, end this now. Having a mobile phone as a teenager is a decision they make and they should fund themselves - i.e. purchasing credit from their own money. There are great prepay plans out there. Its time to get tough - we are in a recession and you are struggling to feed your family.
Do you have Sky? What about Broadband? If so, what costs/ plans?
What about cars - one or two in the household? If its two, how necessary is the second? You mentioned you moved closer to schools in 2005 and so a car should not be needed for school runs. Look to sell the second car and cut down insurance, tax and petrol costs.
You outline education costs of 300 per month for uniforms, et al. This is a very high costs, and while you have 4 children that need to be dressed and sorted for school, you need to get the most out of uniforms where you can - mending, sewing, you know the drill. I know in terms of cutting costs on uniforms, buying shirts in Penneys or Tescos in the colour the uniform requires saves an awful lot and theres not a big difference. If you have girls and there are tights needed (as we had), Penney's do packs of 5 black dernier tights for 3.50. Tights don't tend to last long for girls and I know in my local I would spend at least 3.50 for just one pair in an emergency.
Also take a look into the schools Book Rental Scheme if there is one - when I was a teenager and working, I covered my own costs for my own books through this scheme. The books had to be maintained in good condition and given back at the end of the school year, but it saved my parents a few hundred euros without a doubt. It only cost me about 40 euros at the time - that's the cost of one science book now. I don't know if its in every school, but definitely ask in the secondary schools.
The most obvious thing here is that you yourself need to get a job. Part-time, full-time, childminding, anything to bring money into your home. Your youngest child is 10 years old, and there is no minding anymore. I cannot understand how you are at home when your children are almost raised and can help out with household chores that you would have been doing when they were younger. You have time now to work, and a financial requirement to do so. Age has nothing to do with it. My mother works part time and childminds and is very happy doing so and is older than you with all of her children grown. Look for part time work in a local supermarket, or if you do want to remain in the house, look into childminding to boost your weekly income, or ironing, there's lots you can do. Have you any skills that can help the household financially? One example, an Aunt makes amazing crocheted baby blankets, excellent quality. She sells them to a local boutique who in turn sell them on to the public and it boosts her income.
Finally, a big household clean out of any items ye don't want or need, and head to a car boot sale to flog the lot. Unused DVD's, Games, Books, Baby clothes, dolls, toys, everything and anything. You'll be surprised what you can make and you can enlist your youngest two to help you with it.
)? How did he/you get a mortgage that ends 13 years after he has to retire?