I'm a dab hand at setting mole traps (you should be able to buy them from a hardware shop):
Between mole hills find the tunnel by digging a little hole (just enough to insert the trap) and position the mole trap so that when he (or she) hits the ring the jaws snap shut. Make sure no light can get in though by "gently" covering around the exposed part of the trap with grass and such like making sure you don't prevent the trap from springing. Within a week you should have killed them.