Thanks guys, I eventually found the 205 flight manual online.
The quick comparison I did worked out hourly rate wise is that the 205 will run at $450/hr more than the B3. That is with the expensive prices of fuel in Africa.
What I did see was with the 205 you can add a ferry tank and have 100% in the mains with an additional 280litres in the aux and still be able to lift our system. That will take the endurance up to about 2.9 hrs. Where with the B3 we can't get more than 1.5 hours endurance out at this moment. For us it's all about endurance, the longer we fly the more we can do because of being so far away from base.