It's been a few days now, and Lib is sleeping brilliantly!
I'd say self-soothing is definitely worth a shot, if you're in the same situation. Lib still wakes up occasionally, but I just calm her down, lie her down in her cot again and stroke her hair until she's settled. The best thing is that Lib has learnt that it's normal to be in her cot to sleep, so when it's bedtime, she'll go down even if she's awake and just chatter away to herself until she drops off.
A full nights sleep again is very much appreciated!! :)