Hi Girlinthesticks,
I’m no solicitor, but I would presume that you can deny access if he is using drugs. It would be irresponsible of any court to make a child spend time with an addict. You know as well as I do that they are irrational and can be irresponsible.
I’m not in the same boat as I’m still with my husband and he is clean, but part of the reason I stayed when it was bad was the fear of what might happen if we split up and he had contact.
When he was using I was literally like a single parent anyway, I couldn’t even ask him to collect her after school in case he was high, and I never went out for an evening, even a for a short time, because the irrational fear of what could happen if I wasn’t there and he was in sole charge consumed me, there was no point going anywhere, so I just became the sole caregiver. So I can understand your worries.
Have a chat with a solicitor, they’ll mostly do free consultations, then you will have a clearer view of your rights.
Sending hugs x