sonrock, I agree with dafos. In your room, which I assumed was the standard UK construction, i.e. brick, I would definitely sit in the near field. I would also place the speakers on the wall that is either opposite to the fireplace, if that is possible, or on the fireplace wall.....sitting as far forward of the fireplace as possible and with the fireplace centrally spaced between the speakers. Unfortunately, you sir, have a tough room.
BTW, You might want to look into some great bass traps: The Real Traps Mondo Traps come to mind here.
BTW, You might want to look into some great bass traps: The Real Traps Mondo Traps come to mind here.