It is not up to the poor householder to buy the neighbours a goalnet, or to worry about the neighbours' kids and where they're playing in any way. If they play in their own garden, fine. If they start damaging your property (fence or flowers), or creating a noise nuisance (ball against fence, or shouting obscenities), not fine. If the parents call you a muppet and refuse to cooperate, definitely not fine!
The sound of small children playing next door can be delightful, but there's no need to put up with nastiness or abuse from them or their parents. If you've tried talking to them with no joy, complain to the Council ...
https://www.gov.uk/how-to-resolve-neighbour-disputes/complain-about-noise-to-the-council
... or to the Police if things get violent, threatening or abusive:
https://www.gov.uk/how-to-resolve-neighbour-disputes/call-the-police