Hi there, some good questions, don't feel daft! Its a minefield all this feeding malarchy.
I breastfed DS for 7months and will hopefully do same for this one.
I agree with MumNW on all her points. Expressing is a great thing but we would use it more so that hubby or anyone else could give a feed and it also gave me a bit of freedom to go out for a few hours when I needed to once we were well and truly established. But I didn't ever take expressed BM out with me.
The thought of BFing in public before you have even had your baby is pretty daunting and I was absolutely convinced that I would not be doing it as it was just too embarrassing HOWEVER, once you get established you'll be amazed at how discreetly you can do it. I ended up feeding all over the place, its very easy to find a quiet spot in most cafes etc and places like Boots and Mothercare and others do have feeding rooms. It is SOOOOOO much easier than faffing with bottles and is the beauty of BFing that you can do it anywhere.
With DS 1 I did buy some small Nuk bottles and some aptamil JUST IN CASE. DS must have had maybe 2 bottles of formula in those 7 months? one of those was in hospital and due to him not latching on, being jaundiced and damn hungry and the other was due to me having to go to hospital (unrelated) so I would say that it isn't necessary to have forumla in but it wont hurt. Don't buy a big tub of the stuff though, as we did this first time around and it didn't get used, by the time DS went onto formula he was ready for the next level. The ready made cartons are great though and I have got a couple in the fridge already just in case.
Lastly, just another word of advice BFing is hard, especially in the early days, I was shocked as to how much we both had to learn to do this and it wasn't just a case of showing the baby the boob and hey presto. It took us a good 3 weeks to be really happy and comfortable with it BUT it is so so so so worthwhile, so do battle through those first few days and use all the help you have around you midwives etc. There are some great helplines too, NCT etc.
Best of luck