I’m not sure OP has been totally clear if all standard expenses of living have been covered before the £300. Other people have asked about funding cars, pension payments, any insurances etc.
But assuming everything else has been covered, if £300 is purely for leisure, it doesn’t sound too bad to me.
You probably wouldn’t manage holidays (maybe one of those sUn cheapies) but what do people spend it all on? In a typical month, there might be a few coffees and cakes out, maybe 1 takeaway and 1 meal out, a class or 2 for the kids, a couple of magazines or books, maybe a download of a couple of films if you do t have a streaming package, perhaps £50 on average for household items needed?
Am I miles off the mark?
If there is loads more spending on some of these things, it should be fairly possible to reduce takeaways, eating out, coffees etc.
I agree that you need a contingency fund for break downs of white goods (unless the landlord provides) and those bigger expenses which crop up. Even if you saved £50 a month it would be better than nothing.
The thing is, I suspect that when you say ‘all bills’ are covered, you’re not including all those monthly essentials and some of them are coming out of the £300. For example, have you included clothes or new shoes for the children, or costs which crop up less frequently but are still vital for funding life?