ok so miah went through a stage of being a brat about a month or so ago where she would bite everything, pee on my sofa and be really teritorial about her areas.

This all stopped and it was bliss she was lovely,

But last night i let her out of her room and she was had transformed back into the bratty miah could this mean she is in season???? If so how long would this be likely to last??

if she is not spayed you may want to do that. my lilly got spayed but is still bratty as ever. she is ultra territorial and desructive. however this is supposed to change once her horomones calm down. i suggest getting her spayed as you don't know how long it will be otherwise otherwise.. plus, it is good for their health!!

I'd echo what Lilybear mentioned - is Miah spayed yet?
If not - it really is important to have her spayed once she's old enough (about 5 or 6 months). It is important healthwise, as 80% of unspayed females get uterine cancer. It also will really help with her hormones / behavior as she'll become less distructive and better with using her litterbox.

If she's already spayed - has anything changed in the environment? did any new pets or people come into house?

Female rabbits don't really have a season as they ovulate  only after the male has mated with her.  In the wild, the mating season happens when food is plentiful, but it doesn't have anything to do with their own hormones. That means there isn't really a  time when a bunny is heat. 

Have  you been around any other animals?  Could you have brought home a scent that has made her feel like another animal has tresspassed?

I also echo everyone else's questions and comments regardind spaying.