Hi Hayls, I have a 29 week old ds (still bf) and a 27 month old dd (bf for 12 months), and I have expressed both times using the Avent pump. I think I'm lucky as I've always found it easy (flip side of this is having power shower boobs and lots of leaking). I always found it easier to express first thing in the morning when I was slightly more full, not much as my ds/dd had 4 or 5 feeds in the night at 8 weeks, lucky you with your sleepy dd! I found that is ds/dd were close by then I could express more easily.
With ds I was more organised and I expressed quite a lot from 6 weeks to about 16 weeks and built up a good supply. I've been using it mainly for his morning cereal and for the odd time I've been out. I've saved it in 100ml lots this time as I found it's far better to save lots of little amount than defrost a big bag and then have to throw some away; with smaller bags you can always get another if you need it and there's less waste. I got into a routine of expressing every morning just to get a supply in the freezer.
With my friends there have been some who really struggled to express and some, like me, who found it dead easy, with no real rhyme or reason as to why, good luck with your expressing.
BTW, yesterday I found dd with the pump in hand, trying to express from her tummy and saying, 'No milk mummy, pump's broken, mummy mend it', how do you explain that one to her?