Thanks Lensman, heh. If you had said so earlier I wouldn't have had to bother DreamHost support, but all's well that ends well in the end.
It was pretty simple yes, I hadn't realized I can still 'host' the domain with DreamHost whilst switching off the webhosting service. Well, I had actually looking for a way to turn off webhosting by clicking the 'edit' button. And I didn't find any way of making it not host at the very least a 'coming soon' page. So I assumed there was no way to turn it off without removing the domain from my DreamHost account altogether, basically also removing the email etc. I had TOTALLY missed that there were TWO 'delete' buttons per domain in the manage domains screen, the big obvious one, and the one in the webhosting column which I somehow didn't give any thought to. At any rate, using this button removed webhosting for the domain on DH and as such, got rid of the 'uneditable' DNS records that were causing the problem.
Thanks a lot everyone for your time and advice, I'm glad everybody reaches the correct site now. Otherwise the PR campaign we've started would largely be a waste.