Hi latte, sorry to hear that you're having such a difficult time at the moment and that your experience of mh services is adding to these difficulties. Good to hear that you're using Sane's helpline and the Samaritans to help you cope at the moment. If there's a Samaritans office near you, you can also have face-to-face sessions there (but I don't think it would be with the same person each time you go).
Apart from that, the only other thing I can think of to suggest at the moment is keep going back to your GP, if only to let them know that you're still struggling and the mh team are simply passing you from one unhelpful person to another.
Are you getting much sleep at the moment?