It's hard to speak about how things are in the UK; I'm in the US.

But... In my case, I was not diagnosed when I had a major meltdown at work and quit my job. I was teaching, so I broke a contract and eventually lost my certification.

I spoke to a psychiatrist later who told me it was a shame I wasn't getting help at the time. I could have been placed on medical leave and not lost my entire career.
Take care