The best people to ask would be Air Atlantique/Atlantic Airlines at Coventry who operate Daks in the reconnaissance role and I think they have one configured for pax as well.
For info their phone number is 024 7676 2222.
You must also consider the costs of getting an up and running AOC, liability insurance, Eurocontrol Nav Charges etc. etc.
Sadly the number of grass runways (licenced ones anyway) are on the decline.
I'm sure you must have heard the saying if you want to make a small fortune in aviation then start with a large one!
Rgds PoC