I hope your baby is OK. Your experience does sound horribly frightening, but I don't think anger is the right resonse. In a very rural area one simply cannot expect an ambulance to arrive quickly, or for ambulance drivers to know each and every tiny unadopted road.
Please excuse me if what follows covers matters you already know - or if, because I seem to have taken ages to type this, other posters have said similar things already:
I live in rural Scotland. The nearest ambulance is stationed about 1.5 hours drive away. (Air ambulances can't be relied on 24/7, because of darkness and wild weather.) The land ambulance has to cover a vast, rugged area from that point and it obviously can't be in two places at once. So we have first responders www.scottishambulance.com/YourCommunity/responders.aspx. These are well trained people (some up to paramedic standard) who live locally, know the area, drive a van containing a lot of very useful kit - oxygen, ECG machine, defibrillator etc etc etc. They have walkie talkies which usually work even where there is no phone signal. You call them in an emergency either via NHS 111/NHS 24 or by 999. They turn up to help while the ambulance is on its way and have saved many lives - although most teams are not trained to cope with babies (for good reason - it's a specialist area - but maybe that is something to try to change).
Also while waiting for the ambulance, it is sometimes possible to talk to a duty doctor or to get him/her to phone you - there will be one, though it can take persistence to get though - on NHS 111/NHS 24.
(All is not perfect with this system, however. The NHS relies over-much on very, very dedicated people who give up their time as volunteers or for low pay but take on huge responsibilities. In some areas, there are simply not enough local people willing or able to act as volunteers. Ideally, there would be something like an out of hours doctor or nurse practitioner on duty in each remote locality, but the NHS usually says it can't manage to recruit them. And even then, they might easily take the best part of an hour to reach you. Our GP's surgery is an hour away by road.)
Doesn't Wales have a first responder scheme? If there is not yet such a scheme in your parent's area, can you/they/the local community campaign to start one?
There are also larges notice in GP surgeries telling people to make sure that their houses are clearly named/ signposted, with big clear letters that can be read from the road and in the dark.
As an earlier poster suggests, it's a good idea to have a card with the grid ref of a remote house on it. Also - because in an emergency, people sometimes get flustered and don't communicate clearly - to have a clear, brief, simple set of instructions to be read out over the phone telling emergency services how to get to a house from the nearest road with an A or B number. This helps not only an ambulance but police and fire services, and also delivery drivers, and even the AA.
Living down an unadopted road is just part of remote rural life, I'm afraid. It's a balancing act - which do you want more: peace and quiet or quick communications? The two rarely go together. (In my experience, the answer to that question can change, at different stages of a person's life. ) In the current financial climate, I can't imagine any council being willing to adopt a road they don't already own.