Danni - I've got a pocket nappy with hemp booster & I reckon it would do over night with one. I haven't tried it yet, but I do have 2 hemp boosters as well as some micro fiber inserts, so when I start using MCN's over night I'll just double up.
I'm only using terry flats over night atm. With a booster, or insert for extra. Leakage isn't too bad. This morning was the first time his body suit got wet & thats only coz he slept in.
Even though she may start TT in the next 6 months or so, neither of my girls went without nappies through the day til they were 2.5 - 3 & Bri is still in night nappies at nearly 4. So you should be able to use them for a while.
I'm not planning more bub's, but still think it was worth the change. They are great.