I wasn't sure if I could tag you all in or not, so I left it, but I hope you all get to read this.
This may be a bit long, but first I want to thank you all for the info you have given.
Before we had the ensuite redone, we had carpet in there, but because it was old, it had been worn down, as was the carpet in the bedroom, so the gap at the bottom of the door was enough to let air in.
When the ensuite was redone, my wife picked that lino that looks like wood panelling, or what ever, which meant the floor was ever so slightly lower again, and the door didn't need to be cut (the bedroom door opens into the ensuite)
When it was finished we had new carpet put down in the bedroom, and my wife chose thick underlay plus a thick plush carpet.
Because of that, when you close the ensuite door, it butts right up against the new carpet, and the carpet is in fact much higher than the bottom of the door.
So there's no fresh air getting in to replenish the air the fan is trying to suck out, (which that bit of info was explained to me on here)
So we need to have the ensuite door cut down as if the door was opening in the opposite direction, into the bedroom, and enough so it would go over it, which would leave a gap again under it...if that makes sense.
The door from the landing into the bedroom, had to be cut quite a bit, as you couldn't move the door at all.
So once again, thanks for all the info.
I am still looking for another fan though, as I want a back draft feature on it, so no cold air is getting back into the room when the fan is off, and your bum cheeks don't shreek when you sit on the toilet seat.