I was in a similar place to you last year. I told my then partner I was having suicidal thoughts and, after telling me they didn't count as I didn't end up in an ambulance, they left me, because it was making them anxious.
To be left when you are at your lowest mental state is soul destroying and feels like the worst kind of abandonment. You give love and a large part of yourself to someone and they do that in return.
Fast forward a few months and, I'm not going to lie, it still hurts and I'm still soul searching, but literally everyone I've spoken to about it have been utterly shocked at my ex-partner's behaviour. It says a lot more about your ex-partner than it says about you. And it has taught me that my ex neither loved me nor deserved my love. I hope you come to realise the same for yourself.
This is not your fault and you deserve so much more support from a partner. There is always the opportunity for them to help you through that initial crisis and then discuss leaving, but to do it straight after a suicide attempt is cowardly and self-absorbed. Coupled with the way he talked about you with his friends, he sounds utterly unpleasant and not worth anymore of your time.
In terms of the SS referral, I had one for suicidal thoughts too. And it was nothing but supportive. They wanted to make sure I knew the support phone numbers (Samaritans 116-123, also alternatives here: www.mind.org.uk/information-support/guides-to-support-and-services/crisis-services/helplines-listening-services/).
They also fast tracked me a GP appointment and stayed around until they could allocate a family support worker. And that worker checked in every week and just chatted with me about what had happened, she checked in with the kids and discussed how they were feeling and we talked about their future and everything I had to look forward too. Honestly, SS and family support were a godsend when I felt so alone and definitely helped me reframe my view of the rest of my life in a more positive way.
You have done nothing wrong and you will get through this. Take help that's offered and you may find support you needed from this SS team.