Sugar, bicarb. Nigella has a recipe - calls it something ridiculous though (Hokey?). Anyway, basically it makes Crunchie minus the chocolate, so not quite as good but you're closer than someone with no Crunchie.
At 36 weeks pregnant, you're quite justified in getting him to go back out for confectionary of your choosing.
It most definitely was for him, as I just turned to him before starting this thread and said 'did you really just buy yourself a crunchie bar and not pick me up anything?' He looked very sheepish and said oh god that's really bad isn't it. Twatola.
I know how to make it hassled, it's a piece of piss. But I've just finished making him a lovely dinner, as usual, so would've liked a little gesture of choccie