Atmospheric Refraction and seeing stars below the horizon

[Matt1979]

I have been reading recently that atmospheric refraction can allow stars below the horizon to be briefly seen - I am not too technical with details like this, but I have read in an Astronomy Now publication about the constellations that an astronomer in Start Bay, South Devon, saw Zeta Puppis briefly on a cold December night due to atmospheric refraction.

How many degrees below the horizon can come into view with this effect? I have been using Stellarium to see how much more of the southern sky can be seen from Jersey and Les Minquiers (which are a small group of islands south of Jersey and the most southern point of the British Isles in case not everyone has heard of them). I noticed that the lowest star in Columba (Alpha Columbae?) is only just below the horizon from the Channel Islands, only around as far below as Zeta Puppis is from south-west England.

Would it be possible, then, for one or two stars below Alpha Columbae to come into view from Jersey or Les Minquiers, such as the stars at the far northern end of Pictor, or would they still be too far south?