I had to rip :(
My gauge was too tight, I had a whole extra stitch to the inch. I tried it on, and it did go round my head, but it was very tight, and I don't think it would really have worked. I was trying to convince myself that it would all work out when I blocked it, but then I reminded myself that "it's only knitting" and ripped it all the way back to the beginning to start again.
I suppose it's only to be expected that my gauge would be different as I'm doing something new. Apparently I knit super tight just now, but I'm sure it'll even out in time. In the meantime, I went up to 4.5mm needles, and just started again. It looks much more like the correct size now :) But 4.5mm needles for DK weight yarn just seems insane to me on some level! :D
The knitting also went much faster the second time around. I think I'm getting (!) used to this type of knitting, and I'm still super excited about it. Trying the little band that I had made on also made me excited about the hat when it's finished, I think the colours go together quite well. So, even though I had a sad face at the beginning of this post, I'm not really sad at all.
One thing for anyone else out there trying stranded knitting - if you have to rip back to the start, do it one row at a time! The two yarns get very tangled up if you try to pull out about ten rows then wind it back onto the ball. I would tell you to ask me how I know, but I think you can imagine ;) It was not pretty!!!