Good recipe, some extra tips..
1) You need to be careful of temperature shown. Soft Ball (i.e. Tablet/Fudges) is 112-116C and Firm Ball (i.e. Caramel) is 118-120C so once you reach 116C reduce the hob temperature to keep it around there, if it creeps up too far then the tablet won't set (a darker colour will also indicate too high a temperature).
2) For lazy people like me I find an Electric whisk works very well (but probably not if you are using a non-stick pan!)
3) Before adding the vanilla essence ensure the temperature has fallen below 100C otherwise it will simply boil off!
4) For an improved vanilla flavour plan ahead, put your sugar in an airtight container with 2 split vanilla pods some weeks (or even months) before you plan to make your tablet. It will improve the richness of the flavour.