43 BMI + Non-Alchoholic Fatty Liver Disease?

Hi, I have recently asked my doctor about weight loss surgery after having struggled with my weight for around 10 years. I have tried seeing several dieticians, Weight Watchers, calorie counting, medication etc and nothing seems to have really worked (I either lose only a couple of pounds or I lose quite a bit in a short space of time and then gain that back and more). According to the specialist I see in London, my non-alcoholic fatty liver disease, borderline glucose intolerance and insulin resistance makes it harder for me to lose weight, it isn't an excuse but it means I have to work twice as hard to burn off whatever I eat. However, my liver would get better if I lost weight, so weight loss surgery seems like the only option now. I have a BMI of 43 and, from what I have told my doctor, she agrees and will refer me once she has checked over my notes (she has only become my GP recently). However, I am worried I won't be approved. As I'm in the UK, my only real choice is the NHS, and they say a BMI of 35 with comorbidities or just a BMI of 40 means you fit the criteria. Unfortunately, the NHS has been getting stricter recently due to lack of funding and I have heard many horror stories about it, so I'm really worried I won't be approved. I am also young, I will be 21 in August, and I just get a feeling that people will think I'm not old enough to make this decision. Does liver disease count as a comorbidity? Has anyone else had any experience with the NHS?