I've finished the mission but can't get Nalia to offer me the stronghold,am I doing something wrong I've got a level 9 paladin but have also tried with level 9 fighter, do I have to be a higher level?

Nalia's keep is available only to fighters. The Paladin Stronghold is Sacred Heart or some such thing. So an on site search for strongholds, there's got to be a bunch of lists for who gets what by now.

You won't get it if you're a paladin as Zenith said.
You should've got it if you were a fighter.