I'd toss them in the boil and use them as yeast nutrient.
Muntons yeast does not attenuate too well, you would be better getting a different yeast. You might want to save them to use for an emergency (making a quick brew with no other yeast available, or use if your primary yeast is dead.
If you use this yeast and you end up with a sweet beer, it is not always as simple as tossing in another pack to finish off the beer. Once there is alcohol in there, it is a hostile environment for the yeast.