On the plus side, she went back to sleep until 6.45 - and woke up in quite a good mood for about 20 minutes!
She had a total meltdown before her lunchtime sleep, but went on to sleep 1h45. I put her down at 7.15 and didn't hear from her again - I'm guessing she went to sleep at about 7.45 again (I have been obsessing so much about exactly when she goes to sleep that I decided to leave the monitor in a different room so that I couldn't
) so we'll see how we get on tomorrow. I have to say I think this is working - thanks for the help and support.