Please help..is there anyway to get out of this fight quickley without losing half of my party...I am getting killed by the clones to say nothing of the critters brought up by Jon..any help greatly appreciated as I am close to quitting this game in frustration...thanks...

Did you talk to the inmates of Spellhold before you went to the fight?
They will help you against Jon and there are some quite good mages among them...
Other than that, what level's your party?

SPOILERS:
>
>
>
>
>
>
>
Try to take Jon out ASAP, have your mages cast magic protection removal spells (eg. breach, also detect invisibility if he turns invisible) and let the tanks (and range attackers) hack away. The clones should not be too tough, afterall, they have nothing on them and they are there to distract you from Jon.
MORE SPOILERS (read on if you want advice after taking Jon out):
>
>
>
>
>
>
>
To save your frustrations, once Jon has been dealt with, he will escape. At this moment, be prepare for a not so present fight as Jon's assassins (murderers) begin their backstabbing. As soon as Jon leaves the lab, have all your mages and physically weaker characters go to the NorthWest corner of the lab, and you tanks should be between them and the main area of the lab. Have your mages cast spells like true seeing, and then throw all sort of area effective spells like web, stinking cloud, cloud kill ... etc into the middle of he room. That should make your life easier.

Thanks for the responses, I did have the prisoners with me, and my group is such: Minsc level 11 Jaheira level 9 fighter, level 11 druid, Aerie level 10 cleric, level 11 Mage, Me, Cavalier level 11, Mazzy fighter level 10, and not the least Imoen Mage level 11, thief level 7..Thanks for the spoilers, I'll try them, I think the clones were confusing me, you are right they are quite a distraction...thanks again...