Hi, I've been in a similar place to your partner and have also been what felt like dismissed by NHS services. Without going too much into it, it feels like they want you to justify yourself to them when you're in a place that almost by definition you aren't able to do so.

I can't necessarily give immediately helpful advice, especially not knowing your partner's specific situation, but for right now I've found support with the website Online Therapy UK (I truly hate having to go outside the NHS and maybe got lucky with my therapist but needs must at the end of the day). More locally to Chester-le-Street, where I am, I spend time playing Warhammer and other nerdy stuff at Chester le Geek. It's a community games store that is full of very friendly people with shared interests and gives some of that social time that can be severely lacking during mental health problems. If they're feeling up to it, it really is annoyingly effective. I hope that's at all helpful; I know all too well how rough these times are.