I have had two children here in Sydney (am a Brit abroad) and was overwhelmed with the support available to mothers with young children which, I understand from friends, is just not available in the UK.
There are two organisations in particular (Karitane and Tresillian) which have been the life-savers of many a mother I know. Karitane has a 24 hour support line which ANY MOTHER with a child under 5 can call with any question and get a kind and helpful counsellor to advise them. This organisation also provides PND support groups where the babies are minded by volunteers while the mums get support and therapy (all free by the way). I took advantage of this service when I was diagnosed with PND and, alongside the maternity hospital support staff (lactation consultants, parenting support staff, physio etc) got me back on track in a very short space of time. This was all through the public hospital (not private insurance etc).
Tresillian is another organisation which one friend referred to as 'baby rehab' as you can either have a day visit or residential stay to help mothers (and fathers) get their babies in to a manageable sleep routine. As any new parent will attest to, the sleep factor is a significant decider in daily mental health and to know there is an organisation you can visit and stay with to help you is an enormous help and sanity saver.
In addition, the Early Childhood Centres in each suburb provide weekly (or whenever you need it) advice in the early weeks and months (and will see your child for developmental assessments until they are five) and organise weekly mothers groups. I am not a joiner-iner by nature but these groups were amazing in setting up networks and friendships both for the mums and later the kids.
I guess the point of this message is to say these things exist, to ask if you have such access to support services where you are and if this really is the Mumsnet election coming up, use your power to get the services all mothers need and deserve. Another point is, I suppose, that these services are not dependent on having PND but help alleviate the isolation many women (and men) feel on becoming a parent and the huge adjustment that has to be made.
Look forward to hearing anyone's thoughts on this.