jenny - but that is what they do! it is easier if you work with what you've got than try and mould it into what you want. So if you know you need to go out at x time, start an hour earlier so that there is time for all the intriguing activities up the stairs, you won't always be able to do that, but if you build it in mostly, it will save frustration.
It is also much easier if you just laugh most of the time. If they put a coin in their mouth, laugh and say, that's a bit silly isn't it? Why don't you pop it in the box? (as suggested above) etc. Think how you feel if someone speaks harshly to you, or demands you jump to it - it creates resentment, you want to create willing co-operation, a sense of, we're all in this together. Divide stuff up, eg, you go and put x away, and mummy will y, then we can all z. They love to feel part of things and that what they does matters.
My dc are 13 and 11 and I have never applied sanctions like removing computers, no tv etc, because they are irrelevant. They are about power, look, it says, I can do this to you and again breeds resentment. If they do wrong, have a nice chat about it and why it was wrong, they are much more likely to see sense and think about it next time.
Alternatively, put them in a cupboard until they're 18 and have a large glass of wine!