Transatlantic charter costs?

[I have control]

Can anyone give me some ballpark advice about the costs of a transatlantic charter? (chartering the whole aeroplane - in the range 150 to 400 seats).

It would be from a UK airport to midwest USA, approx 8 hours jet flying during the height of the summer (july/august), ideally nonstop. Return journey 9 days after the outward trip.

I am interested in the approx cost per hour (total cost) and any recommendations for companies to approach.

Thanks for any help