I called the birth centre, who said call the hospital, so I did.

I was promptly told I should have called them and gone in last night (but they'd never told me that before, nor did I really think too much about it last night)... I am to come in. Well, not now, in about half an hour. They then let us wait another half-hour outside the labour ward... so, is this urgent or not? Turns out it's glycoslochia (and I do know that's not how you spell it, any correction would be fab!), but my cervix is all soft and opening, so that's one good thing to come out of it.