Oh wow this thread could not have come at a better time, thank you Waiting for starting it and everyone else for the advice. I will work my way through the reading. Waiting I hope you get the help you need.
Beautiful - what you wrote could have been written about DD (6, in yr1). She is funny, happy, loves life. But I sometimes feel like she's on a different planet. She simply can't stick at any task if it doesn't engage her, and will even get distracted midway through putting on a piece of clothing. Super impulsive, and will regularly run off with no thought of telling us where she is going, or her safety. Barely notices other people are around and will lean on/step on strangers regularly because she's in a world of her own.
Her school work is ok, but she often gets in trouble for not handing in homework, chewing things, not listening (even when she actually is listening, she doesn't look like it because she is fiddling and staring into space).
DH and I are at our wits end because the simplest of tasks like going out or tidying up are a major struggle, and we often end up shouting at her out of frustration. Then feel terrible because deep down know it's not her fault, but we don't know how to help her 
We have seen an ADHD parenting coach a couple of times but she mainly seems to advise constant praise for good behaviours, which is only getting us so far. DD enjoys the praise and it makes us feel more positive, but it never seems to alter her behaviour.
School sees a problem and "ADHD traits" but her teacher actually advised against getting a diagnosis, as she feels that children who get diagnosed often then use it as an excuse not to do things, or to do things badly. MIL has also noticed a problem but is terrified of us getting her diagnosed and stuffing DD full of drugs
. I also worried about the multiple settings thing because she is worst at home but ok at school.
So we stopped considering diagnosis or even talking to camhs but now I'm wondering if we've got bad advice? Either way we need some help - can anyone advise where we go from here?