I can recommend NOT using poison.
My experience of it is that the mouse doesn't just eat it there and then, and drop down dead nice and cleanly on the spot.
They distribute it around and horde it in any nooks and crannies that might be there. Storing any suitcases in the loft? Expect the pockets to be full of rat poison. Anything with any sort of cavity will have rat poison deposited in it. In my case it was a golf bag that didn't have all the pockets zipped up. For weeks whenever I reached in there for a tee I'd be feeling these little green pellets.
As well as that, you don't know whether it's worked or not. The mouse could have died somewhere, but you don't know where.
Humane traps are ok, but make sure you check them regularly - otherwise they cease to be humane. I once found one with a mouse in it that hadn't died from the trap, but that had since died anyway of either old age, starvation, or anaphylactic shock from the high grade peanut butter used as bait.
Apparently if you find one with a live mouse in it you are supposed to set it free at least a mile away otherwise it will find its way back.