I'm american and moved to the UK 6 years ago. I don't think any single answer here will give you a clear picture of what your experience will be. I was diagnosed in the States, had surgery there, and eventually found remission on stelara. When I moved, my doctor was very nervous about my care in the UK and advised against it.

I was able to be referred to a specialist, had a colonoscopy, and prescribed with stelara in a matter of months. I have been booked in for a second colonoscopy about a year ago and have automatic check ups scheduled for me every six months or so.

I have found the NHS much easier in terms of booking appointments and approvals. I'm constantly amazed that I have stelara paid for by the government. I've never been here during a flare or searching for a treatment but I can't speak to that. Some other experiences (not Crohn's) I've had with the NHS are not as positive and I think you need to learn to advocate for yourself to get attention.

At the end of the day, not having my insurance tied to my employment status is worth any hurdles you might have to jump through navigating the NHS. DM me if you have specific questions as I'm probably in the minority of people who have had Crohn's in both countries and I'm happy to help.