I have a CS agreed in principle due to anxiety, and am currently ttc.
I found the process difficult as, if you are not pregnant, straight away you fall outside the normal health care pathways and are something of a freak (for want of a better term). It seems the norm, is that you can't get access to discussing an ELCS without already being pregnant or having previously had a traumatic birth. Most places, expect you to effectively take a leap of faith and get pregnant first. Obviously, my personal experience proves its difficult, but not impossible though.
To be honest, I found my GP a bit useless though she did seem to sympathise and take me seriously which I actually think is half the battle. She basically didn't know what to do with me at all, and said to me at the first appointment that she could maybe refer me to a pre-conception clinic, but subsequently said that after looking into it, they didn't do anything that would be appropriate for me. In addition to that I personally did not want to go to my local hospital in my local health authority for a number of reasons, but primarily because I felt they couldn't cater for my unusual circumstances. Because of this she put the onus on me to find out about other options and she would do what she could to help me access them. Fortunately, maternity is the one area of health care where you are not confined to sticking to your local authority and you can choose to go anywhere you like.
The real stumbling block you have is simply that GPs and indeed many midwifes and maternity consultants simply don't understand the issue of fear of childbirth. Many think its a bit of a joke. And don't get me started on how they interpret the NICE guidelines. Sadly, it is true that not all health authorities are allowing ELCS, even for anxiety dispute the NICE guidelines.
Your GP phoning the local maternity department and them telling her that they don't do maternal requests is your first red flag that they perhaps don't understand the problem or how to deal with it. Its also a bit of a clue that the hospital policy is possibly one that is - how can I put this - not the most forward thinking.
In my case, I researched ALL the local hospitals within a sensible distance and tried to find out as much about their policy/attitude as possible. Not that this is easy, as they tend to try not to advertise it to say the least. That said I am dubious about any hospital that says something like 'proud of our low Caesarean rate', on their website as this quite often doesn't tell the whole story (like whether higher risk patients go else where or women are forced into a VB against their will or whether certain groups of women just avoid the hospital because of this attitude). In the end I found a hospital which state that they are committed to women-centred care rather than talking about how you give birth and actually had someone who had something of a speciality in the field. Something I am led to believe is pretty rare, but I do know that this hospital is NOT the only one in the country that has been doing research recently into fear of child birth. (Bad news is I'm not aware of one in your neck of the woods, but thats not to say that one does exist).
I then tried to get an appointment directly with the consultant. Unfortunately letter walked (though the consultant did say that he would have given me one, if he had received the letter). So I went back to the GP, who DID get me a referral despite it not being within the health authority or one that she would normally deal with.
Appointment with the consultant was brilliant. Straight away he said that my request wasn't simply 'a maternal request'. Basically it was his opinion that my request was based on a medical need based on my mental health and that any care I got would take this into consideration. In short, if I have an ELCS it is medically indicated. I was in quite a state by the time I saw him tbh, so I don't think he had any question about whether I was lying or not. And this is what is what the focus within the NICE guidelines is about - recognising that mental health should be taken seriously and not dismissed. (Although the guidelines say you should be allowed an ELCS even if you don't have a medical need anyway which is beside the point). I can not tell you the relief I felt at just being told this and being taken seriously. I burst into even more tears. It'd taken me about 5 years to get to that point.
Given where you are at now, I think you do need to go back to the GP and give it another go... What have you got to loose given the situation you are in? You are NOT being stupid if your mental health is effectively stopping you from trying for a baby. I know this is something that is difficult for many people to get their heads around, but its step one for everyone - health care professionals and women alike. One way or another the GP should be giving you some sort of support with this. Its not acceptable to just phobe you off by saying that the local health authority don't offer ELCS for maternal request, simply because what has happened is that you have now been left in a state of distress where you feel alone and not listened to. They should be giving you SOMETHING to help you - whether that be to give you some form of counselling or to give you an ELCS in principle.
Think about it this way women who have problems psychically in getting pregnant are given tests or even counselling to deal with their problems or to come to deal terms with their situation. Is it so controversial to suggest that you should also be able to access some sort of support too on the basis that your mental health might be in some way preventing you from having a baby? I thought the days of dismissing things as being 'all in our heads' and telling us to 'just get on with it', were supposed to be a thing of the past... You wouldn't be told this, if you were depressed now would you? This is the taboo that needs to be broken and that women who 'feel stupid' for feeling the way they do, need to realise. It might be rare to feel unable to ttc, but its something that exists in much greater numbers than people are aware of and it causes an enormous amount of hidden heartache.
This is where I think its about getting your GP 'get' just how much distress this is causing you and some how getting yourself diagnosed as 'having some sort of problem'. I personally would try and see another GP if there is another one at the same surgery. My gut feeling is that the one you have seen can't be arsed and doesn't understand the extent to which this can take over your life and is a 'real issue' for want of a better expression. Because its so unusual and doctors are just not aware of it, I think that you actually have to be persistent to a certain extent, and have to do a lot of the donkey work yourself to access the care you need. Relying on the GP to find out information for you alone I don't think works sadly.
If I'm being really honest about this though, your biggest issue could simply be your age now. You simply don't have much time (if any) to mess around trying to get someone to get an ELCS agreed in principle first. You may need simply think about taking that leap of faith or finding some way to come to terms with not having children. However going by the threads on here, if you are really that determined to have an ELCS, once you are pregnant, you are 'in the system' and are therefore taken more seriously. If you are prepared to fight the system, then the chances are you will end up getting someone to agreed to an ELCS (And your age would actually go in your favour in this respect). It does happen, but I've seen few women on here not have the ELCS they were desperate for.
I really wish I could offer you more than that, but the truth is, this is an area of care that few people are currently that interested in and few people want to do much to change that ignorance for a whole variety of reasons. Sorry for the long and rambley post... I'm terrible for them! But I hope if you can get to the end of it, without loosing the will to live, that it helps.
Good luck!