It's hard making the decision when to try solids, i wasn't sure with our DD but she was ALWAYS watching us eat, trying to grab at things so the health nurse said we could start her on rice cereal just after 5mths, she started having that an hour after her first bottle every morning, we then slowly introduced a night meal (ie pumpkin, then pumpkin and potato etc).

I found once she started having the rice cereal her morning sleep was a longer as she was more satisfied.

She always slept generally well over night with maybe only 1 feed but as soon as we started solid meals and she got used to it the only time she woke was for her dummy and thats it.

She is now 10mths, having 3 meals a day, an afternoon snack and only 3 bottles and sleeps 7 til 7, with maybe 1 dummy grab at around 5am.
BF babies seem to want a night feed for longer than bottle fed, maybe even a small amount of formula before bed will top her up enough to sleep through?

I hope you have some luck, it's always so hard to decide if they are ready for particular things, every little bit of knowledge helps.