Shumba was like this when he was younger, he grew out of it at about nine months (he is now 14 months) it took a lot of time outs and ignoring his bad behaviour, there was a point when I thought he would never learn. When he was jumpy and nippy he was removed from the room into isolation, or everyone left the room, (I found if I was confrontational he would treat it like a game and come back for more). It has got to the stage now where if he jumps or mouths (which isn't very often - only when he gets overly excited) we can just turn our back on him and he gets the message pretty quickly. It is important when you are isolating them that you do not talk to them (harder done than said) they need to know whilst they are behaving inappropriately they get no attention from you, good or bad.
I hope you are able to find a technique that works for you, but I think patience is the key, don't get angry or frustrated they seem to pick up on that. Good luck because they are certainly worth it.