Okay, I have a confession to make. I did cc last night. I just couldn't face another night like the previous 2, not that the ones before that were much better. I did the Supernanny version: Do normal bedtime routine, then put baby in bed and say 'night night darling, go to sleep' and walk out. Leave for 2 mins, then go back, pat her, say Shhhhhh, then leave for 4 mins. Then 6 mins, then 8...
So, DD screamed. And screamed. DH had to physically restrain me - he said we'd give it half an hour and see how we got on. I went back in after 2 mins, and then after 4. She cried and cried - it was awful. Then, after 1 more minute (so 7 mins total), she suddenly shut up. When I went in, she was fast asleep. She woke up 20 mins later and cried again, but this time it only took 3 minutes before she fell asleep again. She woke up again after an hour (so 9.30ish) but only cried for 1 minute. Then she slept until nearly 1
and when she woke up, cried intermittently for 20 mins, but not the awful screaming of earlier, just normal cries and I could tell she was getting sleepier - she kept stopping, being silent for a bit and then starting again. And then...she slept until 7.20am! 
I put her down for her morning nap in the same way, and asked nursery to do it too for her afternoon nap (she's had a couple of nursery sessions this week to prepare her - I go back to work after Christmas), and she cried for no more than 5 mins each time. Then at bedtime tonight, I bf her in the living room, took her into her room and laid her down, she started to cry, but it lasted for 90 seconds and it's been silence ever since!
I felt horrible last night - it really is heartbreaking to hear her cry. Like Scream I'm not exactly advocating it, and if DD had kept up the screams for much longer I'm not sure I would have stuck to it, but she didn't. However, that's the first 6 hour stretch of sleep I've had since we hit the 4 month regression. She's 9 months now.