I had a pet lamb with crook last year. She was reluctant to stand when she arrived and got gradually worse. She drank well and was always bright. The books say give them two lots of ABs after which there isn't much hope. She got them and a lot of TLC and encouagement. After the second round of antibiotics, there was no rapid improvement, but after a time she got more willing to stand and potter about and eventually got over it completely.
We still have her - she's a bit smaller than others her age, but I don't know if that was her condition or her genetics. She's perfectly healthy and troublesome now.
Don't give up!