Shop for fruit, veg, meat at a market - not the farmers sort, but traditional ones. Often loads cheaper, and you can negotiate.
Buy seasonal veg and freeze it
Bulk cook and freeze - especially things like pulses which take a long time to cook
Avoid needing to buy fast food by freezing little portions of pasta sauce, rice, curry. If you freeze in plastic ziploc bags, you can make them as flat as possible so that they reheat really fast.
Buy childrens books, toys at car boot sales, charity shops, or NCT sales. Nearly new stuff goes for pennies
Do clothes swaps with your friends to exchange stuff you are bored with/don't fit into.
Have a girls night in and exchange manicures, hair colouring, even leg waxing if your're brave !