First of all this is my first post in a while so I'd like to welcome myself back! 
I've got an idea for something but I think it would run more then 30 minutes so I was wondering what would be the best thing to write it as?
I know TV sitcoms should be confined to 30 mins per story(for the new writer) but would the radio be the same? Or could I submit episode one of what would be a six part story running 30 mins each?
If not I thought I could try writing it as a novel or even a graphic novel.
Hard to comment without knowing more, but what do you think it will work best as?
Aren't most slots half hour?
Hour long slots are usually one-off plays, I do believe.
It was really hard to explain my situation so I understand you finding it hard to help.
Basically it's a detective story which I feel I would need more then the half hour time slot to tell properly, otherwise I would write it as a half hour sitcom as I do have more stories with the characters which I'd like write.
Anyway, the idea of a hour long one off play is intresting as I'd prefer to write it as a radio play because that's what I'm used to and to write it as a novel would mean a lot of learning on my part.
Also, if it was a hour long one shot story it could always lead to a half hour long series if it proved successful so I might go with that 
Just to let you know, I usually write pilots for half hour radio sitcoms (although I'm yet to have anything made) so this is something a bit diffrent to me which I'm looking forward to giving a go.