Slang. Usual meaning is literally just money, but can be used to mean other things such as "a bit extra", "a bonus", "a waste" or "something spare". For example :
- "I'm earning four hundred quid a week with no overheads : it's all bunce, mate !"
- This would mean that one has a substantial amount of cash to spend on booze etc.
- "I used 20 bags of cement on this last job, but had 5 bunce !"
- This would mean that one has five bags of cement that can be used on another job, but both get billed for them.
Hence, an unexpected bonus.
- "Nah ! Give us some bunce !"
- I would like a tip, please.
- "That's alright - it's bunce"
- This is not needed.