Less trips in the car, plan to do as many things in the same route at once as possible so you won't need to take the car back in the same direction again later in the week.
childcare voucher schemes -- check if your employer has one.
research your shopping costs and shop accordingly -- fresh from local grocers (if that is cheaper), dry goods from ALDI or LIDL, etc.. (Aldi is brilliant, BTW, as mentioned earlier; less keen on Lidl).
take the kids to soft play/swimming etc when the cost is reduced
only by 3 for 2 or BOGOF if you will actually use the item (shocking how much stuff gets thrown away).
Use your Boots card, save the rewards for Xmas or other presents.
Bulk buy kids' Birthday presents when you see good deals (e.g. I recently bought 4 of the same game half price from ELC, saved on shipping that way too and had the presents ready for individual b-day parties) and also from The Book People (bulk buy or individual books are great value as well).
Get a slow cooker (cheap)-- you can cook cheaper cuts of meat, freeze half of it for another meal, and it is also a time saver (might not be so good on the leccy tho).
Buy everything you can 2nd hand.
Conversely, you should invest well in your appliances; not the most expenxive, but mid-range. better to spend £250 on a washer that lasts 10 years than £150 every five years.
Clothes: buy darker colours, few prints, and conservative styles (you can accessorise boldly if you want to stay fashionable). INvest in quality pieces that will last (e.g. wool trousers or cardis) for the same reason as above. get things in the sale that you genuinely think you will wear next season. Develop your own sense of style so you are not swayed by the latest 'must have' trend.
DOn't buy magazines. ever. not only do they quickly add up, but you will be lured into thinking that you need these things in order to feel good. you do not. (OK, one or 2 treats maybe. )
Keep a jar for loose change and save it for something special.
have a direct debit of £10 a month into a savings account, just for rainy days.
Always aim to save at least 10% of your income for your retirement. (we are really crap at this one but it is important)
Hope that helps. We are really feeling the pinch at the moment!