Thanks all this is really helpful, great to get a range of perspectives. Makes you realise how much all the NCT etc info is aimed at first-time mothers and doesn't really offer much guidance for those weighing up the needs/demands of other children as well.
I am having a very complicated pregnancy (was in hospital all summer) and I am very disabled at the moment, which is only going to be worse by the time the baby is born. Realistically I am going to be quite disabled for quite a while after the birth and there's no way I could look after the new baby as well as toddler DS on my own so we are keeping our lovely nanny on through my maternity leave - I'll only be off for four or five months anyway. On the plus side, I suppose this means it will be easier for me to spend a lot of time sitting with DS2 establishing breastfeeding if necessary, but the hormones from the breastfeeding will slow my recovery physically - they did last time and my pregnancy last time, though horrendous, was not as bad as this one.
The other factor is that I had a very severe PND after DS1 and I have been advised by several HCPs to think carefully about breastfeeding - and especially the constant night-waking - from that point of view.
I think DH would quite like us just to decide against breastfeeding altogether, but I don't want to do that - partly because there were (occasional!) bits of it I liked, but also because DS did really love it - he was quite an anxious sort of baby and for the first few months it was the only thing he did seem to enjoy! He was so hungry all the time, quite jumpy/anxious, hardly napped at all even as a tiny baby and still doesn't really sleep through at nearly two, whereas I can see from plenty of friends/family that those early months can be a lot easier with a different sort of baby - if DS2 is a bit less intense and sleeps better, and my mood holds up better, it might all be a lot easier.
I will definitely be doing some degree of mix feeding from near the beginning though so that DH can share the load a bit and so that there's not a big trauma about switching to the bottle if my mood really slips and we have to prioritise my sleep for a while.