IMs are Independent Midwives - fully qualified and often very experienced MW's that have chosen to contract their services individually, outside of the NHS, such that they can provide continuity of care and individual support in a way that is too often prohibited by NHS staffing constraints and policies. Most IMs are members of the IMA and will show up if you search on that site, but I do know of at least one in the area who doesn't come up (keep meaning to ask if that's an intentional omission or not) - if you're interested I'll pm you with details of those I've been in contact with and my impressions :). I think the going rate is around £3k to £3.5k.
Re. your MW's comment that you "wouldn't be allowed a HB", I think the polite comment is that she may need some additional training on the (lack of) authority that she has in this area. Put bluntly, unless you have been sectioned under the Mental Health Act the hospital and its representatives have no legislative power to force you to accept their kind invitation to utilise their facilities for the birth of your child. They can advise against a HB, but it is up to you whether or not you choose to accept their advice.
Women can and do choose to plan a HB following a Post Partum Haemorage (PPH). I'm one of them - but I do know that my PPH was due to a tear rather than any uterine issues so had no reason to believe it would repeat, and it was also gradual rather than catastrophic so not a terribly scary experience.
I haven't come across jaundice (I'm guessing that's why your DS needed to go in the light box?) being given as a risk factor in a HB. I'm not an expert, but I've got the impression that a jaundiced baby isn't an emergency situation as long as the baby receives treatment reasonably fast (ie within a few hours).
HB isn't right for everyone, but it is an option for them (mental health permitting). There are situations where my personal opinion is that a woman would be taking excessive risk in choosing to remain at home - but then depending on her reasons for being interested in HB in the first place what's excessive to me might still not be sufficient reason for a hospital birth for someone else - although that other woman might well blanch at my planned home breech birth of a larger than average baby...
If you are interested in finding out more about HB you might find the homebirth.org.uk website interesting in general, with particular reference to this page, which looks at PPH in specific.
I'm finding it quite bizarre going through maternity care now I've developed additional risk factors. A little digging has made it clear that the statements re. how risky it would be for me to have another HB, represented as hard facts by consultants, often have remarkably little evidence to support them. It makes it incredibly hard to work out what the best course of action for me is.
Things that are important to me include feeling as though I can remain in control of what happens as far as possible (in the sense of being supported to make an informed decision on whether or not to consent to procedures rather than having my care plan made for me and my consent assumed) and having a peaceful, calm, uninterrupted birth - or as peaceful, calm and uninterrupted a birth as is possible with any complications that may arise. I had that for DD1 and although the MWs were as good as they could have been for DD2, being in hospital and not knowing them before hand did make it a very different dynamic and one that wasn't an improvement for me in many ways.
I'd also like to try a waterbirth for once (I laboured in water for DD1, which was lovely, but agreed to get out for the birth as the MWs' (extensive) breech experience extended to land birth only - and had planned a waterbirth for DD2 but circumstances dictated otherwise). One conclusion I've come to is that the only way to be 100% sure of getting a waterbirth is to have a HB, as then the pool will definitely be available. I think my local maternity unit has 1 pool between 8 rooms - I know that's better than many, but it still doesn't strike me as great odds.
It does sound like you had a quite a rough time emotionally as well as physically - I really hope things go more smoothly for you (and your DC!) this time round. If you want more support, wherever you decide to plan the birth, you might well benefit from an IM or a doula (someone, usually female, experienced in supporting women and their families through pregnancy, birth and the postnatal period - they are very unlikely to be currently registered medical professionals, but can provide a great deal of emotional and practical support in a way that MWs, particularly NHS MWs, do not have the time to do. And they tend to be a lot cheaper than IMs!). There are ways to maximise your chances of getting the birth you want and a bit of knowledge from someone who's been there and done it before, and a clear head from someone less emotionally involved, can be incredibly helpful in achieving that goal.
(Oh my word, I've just realised how long this has become. Scuttles away with a 
...!)