Hi Sarah, I am in exactly the same situation as yourself. I have a gastric band and am going to have this removed and a bypass done instead. I just started the pre-op diet this morning and my op is scheduled for 12th September. I am self pay also.
I am an insulin dependent diabetic injecting six times a day and have angina and arterial sclarosis and arthritis - all of which, I am assured, will be improved with the bypass.
The difference between my story and yours is that I have the full support of a large team of specialists who have been absolutely wonderful. So far I have seen the surgeon, specialist nurse, ward doctor, dietician and spoken to the physiotherapist. Had loads of tests done and been advised on all aspects of my surgery, after care, diet and diabetes management.
Everyone is different so you must get advice tailored to your own situation but so far I have been told to cut down on my insulin on the pre-op diet and that after the surgery it will be best for me to stop all insulin but continue to test and dose accordingly and that, with luck I may never need further insulin. If I do it will be a vastly reduced dose.
Yesterday at my meeting at the hospital with the dietician the anaesthatist (sp?) left me a letter outlining which of my medications to continue taking up to surgery and which to stop eg not take my daily aspirin for one week prior to surgery and no metformin from the day prior to surgery etc.
If you are not getting this kind of advise and support I would agree with other people here that you should really look around for a provider who will give you this support that is invaluable. I am under the care of Spire Yale Hospital in Wrexham.
Whatever happens, remember that you are not alone. If it is any help we can be bypass buddies together {{{{{hugs}}}}}