Sorry that you are sufferring and are finding it difficult to get help.
Your experience of the NHS is fairly typical.
The failure is institutional
Without people choosing what to spend their own pennies on, or not to spend them on... The only way that what services will be provided, where and in what quantities and quality can be decided - is politically.
Add to that, price is a rationing mechanism: at an auction for a Rembrandt painting, the price is raised until there is only one willing buyer left. When a shop needs to clear left over stock, ready for the new season's stock, it drops prices, and people que up and even fight to buy what has failed to shift all season at a higher price.
The NHS is "free " at the point of use, so naturally there is massive over demand.
of course, it is not actually "free", it is very expensive, and because there is no entrepreneurial owner who can keep the profits from working efficiently, and because there are no real competitors to lure paying customers away -the NHS uses predatory pricing- there are no incentives to be efficient.
So it is almost certain that we pay far more for NHS services than we would pay on an unhampered market. Incidentally, the American system is still largely a distorted third party payer system.
For the decision making
Individual people are at a disadvantage to organised pressure groups.
For pressure groups, it is easier to organise and hold together a small group than a large and diverse one.
There is also a greater motivation when their is a large reward, than when the reward or cost is relatively smaller.
Hence the decision making for the NHS (as in all politics) is dominated by organised pressure groups, representing relatively small numbers of people who stand to make considerable gains:
Such groups as drugs companies and doctors organisations,
Nursing unions represent a more diverse and poorer rewarded group of interests, but are still a way more politically concentrated constituency than ordinary peons...
Unfortunately, "mental health" represents some of the financially least able in society, and the politically easiest to ignore, minimise, and throw under the bus.
I'm looking to train as a CBT practitioner, but even that is stitched up by professional associations throwing up entrance requirements on new trainees, that existing practitioners never had to meet. Had those requirements been for the benefit of patients, they would have been applied to existing members too. They never are. They are solely to reduce new entrants to the field in order to limit competition and hence maintain prices at an artificially high level, and with feck all quality.
There are good TS out there, there is also a lot we can do for ourselves.
You come across as very bright and motivated, and already well read.
It is important to have a reality anchor, someone of reasonable intelligence, needn't be super bright, but does need to have good common sense. There are people here who can perform that role,
To catch any spirals of negative thinking and drasticization. To validate your experiences, and to cheerlead your real achievements and qualities. Qualities that you will have more of than you'll be likely to admit to yourself at present!
Coming here provides access to probably the largest repository of PTSD experience ever assembled
It also provides controlled exposure, to help you disarm your triggers.
By all means use the sh!tty dysfunctional monopoly that is the NHS (you may for example be able to self refer for CBT, under IAPT), every one else does, it is a classic example of Garrett Hardin's " tragedy of the commons", in which everyone has the incentive to maximise their own consuption, as the benefits accrue to the user, while the costs apply to all.
But do not ever consider yourself dependant on the NHS. One thing that CBT teaches, is how to be your own therapist, and that gaining or important. of a sense of self agency is so important.
It's your recovery, not your miserable little overpaid and over entitled GP's
Feck him!