You state in your original post that you were turning right from the left side of the road, are there two lanes in the direction you were travelling and therefore were you in the wrong lane? If that is the case then the 70/30 offer is probably the best that you will get.
If you were in the correct lane to make the right hand turn, then I would go back to the insurers and claim that it was a Non Fault accident and therefore you should no pay any excess.
One way or another, the RBS group (Direct Line, Churchill and Privilege) should be picking up 100% of the costs and subsequently claiming as much as possible from the Third Party's excess!