UK step parent adoption process??

Hi, just wondering if there’s anyone here who has gone through a step parent adoption process in the UK?

My daughters father hasn’t been in her life much at all, we were together for the first year of her life, she’s now 6. He has drug & alcohol issues, he gets clean for a few months then goes back to square one. 2 years ago my mum had a phonecall from the police saying he’d been in a bad accident & almost lost his life, (drugs / alcohol in his system whilst riding a motorbike). In my opinion he is unfit to be a father. Social services and the police contacted me explaining he should not have unsupervised visits with my daughter (which is fine by me!).

During our relationship he was very abusive, sexually, physically and mentally but I never took it further.

My now partner and I think it’s best for everyone all round if he were to adopt my daughter. But we’re unsure if it’s worth the hassle. My ex does not have contact with my daughter, but I’m worried that if we take it to court then he’ll clean himself up for a few months so that he can regain access to her. That would be my worst nightmare!

Just after some advice if anyone else has been through something similar x