My cry for help yesterday was heard, and thanks to Jessica's tip, I whip stitched the triangles together and it worked like a charm.
I'm so thrilled! My first ever crochet project is finished. Or is it?! I may make the scarf a wee bit longer... But for now I'm absolutely over the moon and so happy with the scarf.
And a bit sad that it's done; I need to find something else to crochet now. I suspect I may jump on either the ripple or the granny square (or why not more triangles?!) wagon.