The UK system is very different from the US, mostly fortunately, as far as I can tell from various posts on here.
As soon as you have a National Insurance number you can get free treatment on the NHS. I am not sure at what point in your move you would get one, but if you're moving for work they often help you get one before you arrive. You then need to figure out where you will be living and get an NHS GP near your house. The GP will be your primary point of contact for seeing specialists and will also handle your regular blood monitoring (although you may need to go to a local hospital for the actual blood tests). You should ask your GP for an immediate referral to a consultant GI on the NHS. Getting an appointment with the GI might take some time, however. All of this will be free (or free at point of service since we all pay national insurance contributions).
In addition, if you will have private insurance and are in a flare, you can see a private GI (usually with a GP referral). The private GI will, amusingly enough, usually be an NHS GI that sees patients privately a few days a week. Many of us see our GIs both privately and on the NHS, depending on urgency, when you can get an appointment and the details of our insurance coverage. The approach many people take is private is for convenience and control over your time, NHS is for when its serious and/or chronic (it's harder to get appointments on the NHS). I also see a rheumatologist and after starting to see him privately he moved me to his NHS practice, since he wanted to make sure my coverage and treatment was comprehensive and not subject to limitations on what my insurance would cover. My UC is mild, so I am in need of less ongoing treatment (just aza), so I prefer to see my GI privately when convenient for me.
Finally, self paid health care in the UK is much cheaper than in the US. I'd say you should go on the aza and accept you MIGHT need to pay for one blood test and GI appointment yourself in the gap period before you have a national insurance number. the private GI appointment will be £150 and the blood tests will be about
the same (especially if you just ask for liver function and full blood count tests and wait to do anything more detailed). I don't know what your finances are, so that might be a lot for you, but wanted to make sure you realised it's less than it would be in the US.
Hope this helps. Let me know if you have further questions.
Post Edited (FSLondon) : 2/3/2016 2:24:06 AM (GMT-7)