If you do not have a thermometer, you can see if the fudge is ready by dropping a little into a cup of cold water; if a soft ball is formed, it is ready.
Made this but think i didn't get the temp. high enough and/or mix it for long enough. I re-melted it and added some icing sugar (prob. too much) and then used an electric whisk to whisk it as I don't have the energy to beat it long enough by hand. It seems to have set well and quite quickly, a bit too grainy - icing sugar too much of - but tastes divine. Since it was my first time making fudge I think I'll need to practice again ... cleaning up is a doddle since everything dissolves with a bit of a soak in warm water ... that which was left after cooling and not picked off - 18 Dec 2016
First time I made it, it went over the temp very quickly but I ended up with toffee. Second time was a complete success and lovely both times - 08 Feb 2016