Get twelve of the cheap wooden traps from B&Q and place them in known runs, in cupboards the mice have been in etc. Even if you don't have that many mice a lot of traps has a quicker outcome than too few.
Mice tend to run around the edge of a room, so place the bait end against the skirting boards. Sometimes mice will jump over a trap, so placing another alongside the first one can help get some of the tricky devils.
If you think you got all the mice, leave the traps down for another 2-4 weeks and keep checking for droppings etc to ensure you don't have any stragglers.
Personally I'd try to avoid poison as if the mice die in an enclosed area there is a chance they'll start to smell as they decay.