You have felled the tree at a time of year when there is a lot of sap/moisture in the wood, if it had been cut when the tree was dormant then you could reduce the drying time.
I think for 1" decking about a year will be OK, as Scrit says stack the boards with 1" sticks between layers and only cover the top, stack it in the shade not in sunlight.
While you are waiting for it to be cut, paint the ends with a couple of coats of paint, old household gloss will do to stop excess moisture loss from the endgrain.
If you want to get another quote for a mobile mill, try
Scott timber who I get my green oak from or there are a number of mobile mills in the South East listed
here , I've also used Charlie at Treespanner in the past
For any thicker boards get them cut straight through the tree to give you wide slabs, these can be cut up into usable widths once dry.
Jason