Fallacy number 1
Of course you have the right to insist on ELCS if that's what you want.
Unfortunately this statement is untrue in the UK. A lot of people now believe this because of poor reporting of the changes to the NICE guidelines on caesareans but its just not true. You do not have a 'right' to an ELCS. However you do have the right to the most appropriate care for you which may well be an ELCS.
I think you have to really think about what it is that is that bothers you about giving birth - there may be alternatives to going straight to an ELCS, that you haven't explored. Unfortunately these options are not often discussed. I know that the hospital I was at did a lot of work with women who requested ELCS and getting to the bottom of what their anxieties were - particularly with women who had a previous traumatic experience. They didn't refuse ELCS, but were keen to give women who wanted one proper support as are usually in extra need of this. Many actually decide to go ahead with a VB in the end as they were given reassurance and rebuilt the trust they had with midwives that they lost during their first experience.
If you are worried about further damage to your pelvic floor, I think you need to bare in mind that its not just the method of giving birth which can result in problems, but also the actual pregnancy itself. If you already have weakened muscles from a previous VB then you may well be more susceptible to further damage regardless of whether you have a VB or a CS as the majority of damage is done during your first birth. A CS as a prophylactic choice for subsequent births I believe only has physical benefits for some women.
Fallacy number 2
Look at the NICE guidelines. They'll have to go through the process of having a psychological assessment and making sure you know all the risks but you can insist on one.
The NICE guidelines focus on - but are not restricted to - the psychology of choosing an elective, but the fallacy is that you will have to go through a psychological assessment. The NICE guidelines suggest that you should be offered counselling not that this is compulsory. The problem is more than many hospitals have interpreted the guidelines in this way, and do pretty much insist on you going through some sort of process which looks at how this affects you mentally. I do think there is some merit in this, as many women - perhaps the majority - who ask for an ELCS do so because there is some sort of trauma or history that means a VB is a prospect which gives them anxiety. However this is not true of all women, and there are reasons which are a 'lot more rational' and logical in their reasoning for the benefits of their overall health and for whom psychological assessment is completely inappropriate.
The truth is though, that there is no consistency in how you will be treated if you request an ELCS. Its very much up to individual consultants/midwives and the policy of the Trust which you are at. Unfortunately it can be near impossible in finding out where you stand with this before you embark on pursuing getting an ELCS. It can be a real battle, but equally it can be very easy. Its complete pot luck.
Fallacy number 3
If there is no medical reason (which in itself can be subjective), hospitals should follow 1.2.9 of the guidelines - providing perinatal mental health support.
Mental health reasons ARE a health reason. Diagnosis as being a mental health reason can be subjective but mental health is as valid a reason to have an ELCS as physical ones.
As I mentioned above, it can be useful to go down this route as often women who want an ELCS do have underlying issues that are yet to be resolved and need help to address these issues.
In this particular case, it does seem that the OP does have unresolved issues with a previous traumatic experience, so it would strike me as relevant to her to explore this with the mentality that if she is suffering from anxiety she has the right to the most appropriate care to deal with that - which might mean she has medical need for an ELCS.
In the OPs situation, I think pushing for appropriate support and an ELCS would be the way to go at this stage; this means she gets the help she needs and may give herself the option further down the line regarding an ELCS - if she doesn't pursue she doesn't have the luxury of being in this situation. There is no obligation to have an ELCS even if one is granted; you can change your mind at any time.