Plenty of playdates round at people's houses (take in turn to host)
Look on internet for for special offers before going anywhere.
Use Tesco clubcard vouchers.
If going on train with a 3/4 year old, apparently it is cheaper to say they are 5 than just to pay for adult tickets as you can get family ticket . Sounds odd to me, but that's what I was told at ticket office last time.
Keep ice creams in freezer rather than buying from ice cream van.