I've got one now!
Not a first timer: she had a lamb last year and was an excellent, milky mum. This year she has twins and a big udder but seems very unwilling to produce milk. I can express a little but really not much flow at all.
She's a bit dim and very shortsighted which doesn't help. She is favouring one lamb over the other to a point where, given the lack of milk flow as well, I'm thinking I may have to hand rear the other. I've already topped up her colostrum as she really wasn't getting much of a look in. I think was getting disheartened with the lack of flow when she did get to a teat as well.
Will consider getting the vet out to check for mastitis if no improvement by tomorrow, but there is no heat or lumps etc as far as I can tell. Perhaps she's just fed up with me poking around!