fire bricks in open fireplace

I have an open fireplace.
It has a back boiler, but that has been decomissioned.
So the grate area is quite large.
It has been suggested to me that i should put fire bricks at the back of the fire to bring the burning fuel forward.
But i am not sure if that is the right thing to do.
Considering the slope of the back of the fire, i would imagine that it would be better to have the bricks at the front, pushing the fuel towards the back, so more heat gets deflected into the room.
If the bricks are at the back, that brings the fuel away from the back, hence less heat deflection and also it is more in line with the chimney hole, so more heat loss.

What do you think?

If your interested in increasing heat output relative to expenditure on fuel, replace the inefficient open fire with a stove.

whatever about the fire blocks i assume your back boiler was decommissioned by a professional. What i like about an open fire is the look of it and it provides company in a way if no one else is around. Bit crazy i know!

Sid has the right idea; stoves can have glass fronts so that you can see the flames. They are somuch m re efficient than open fires.