ihave a dd who is adhd, but am no expert. being hyperactive means that they can have limited impulse control (so interrupting/calling out etc is normal), but does not mean that they back chat or are rude. they may say what they think without much of a 'filter' but if they are actually being rude etc, then that isn't adhd.
being adhd does not make them competitive - we did a load of questionnaires about dd's behaviour, and the Q's about being competitive were not to do with being hyperactive. and just cos they are very active, doesn't mean they are good at sport - in fact, co-ordination can be a problem cos it requires concentration.
there is no proven link between intelligence & adhd. it can be that a child's intelligence is overlooked, therefore making their behaviour worse as they aren't engaged, but people of all levels of intelligence can be adhd.
i live in the US, so did a load of research online. here, there's a national doctor's website & forum dedicated to adhd. google uk websites to find similiar, or talk to your gp and ask for some info.
dd also has to touch/taste/feel everything, and constantly moves - even when watching tv or reading, her body never rests. she also has some VERY 'hyper' moments when she just can't sit still etc. at those points she is barely unable to process the environment around her, and no learning takes place (we had this happen during a doc's appt. so witnessed her responses changing). Also, she can sometimes withdraw completely, as she gets 'overloaded' when there is too much sensory stuff around her, OR it can send her hyper.
There's quite a strong link between adhd and sensory issues - so often food phobias, can't stand itchy clothes etc.
dd is very sensitive to any discipline & hates being told off. it's a myth that adhd kids are naughty & don't care. she desperately wants to be good & do well, but there are times she cannot control what her impulses are telling her to do - so running across a road, or jumping into the deep end of a pool etc happens as she just HAS to do what her brain is telling her, she cannot pause & control her actions.