For a large floor area, do not be tempted to go to a 'bargain' diy warehouse deal. If you are going for a large format size ie larger than a 600x600mm or a 600x300mm tile. The cheaper deals on these large formats mean that more often than not the tiles 'bow' in the middle or they aren't calibrated.
If you want to go down the porcelain tile route then Royal Mosa, or Porcelenosa are good options. Please OP when you place your order get it in writing that the tiles are to have the same calibration points and are the same batch number. Do not get blinded by salespersons trying to tell you batch numbers do not matter, they are essential or you could end up with a mixed delivery of various shades and mm differences which will make the Tiler's life hell.
Just a side note as you mentioned it's a very large area, you may need movement joint(s). Contrary to popular belief houses move and the movement comes from the substrate to the floor finish. A movement joint will take and allow for this.
Finally and most importantly the tiler. A good tiler will know about the substrate and should do a survey beforehand. Do not let Joe Bloggs loose on your tiling. If the tiler starts to put a few dabs of adhesive on the back of the tile, I can warn you straight of there will be voids under the tiles which in term will crack at some stage. There are some superb tilers out there but sadly there are some abysmal ones, I have been called out too many surveys/inspections on so many failed tiling projects, where the distraught client, has literally handed over money to 'cowboys' only to have the tiling condemned, and that is heartbreaking.
If you need any advice feel free to message me.