Welcome to the Liver Disorders community, you certain have your share of problems. And you've summarized it well. Your Hepatic Cyst and Haemangioma will simply need to be watched. Not much to worry about wrt those two. But your possible Adenoma is a different, troublesome pathology for sure. Hepatocellular adenomas (HCAs) are also known as hepatic adenomas or liver cell adenomas.
First thing to do is to get a positive diagnosis for the adenoma, if they still remain unsure at all. There are higher energy MRI machines (3T to 7T, Tesla) out there that can provide better imaging. There are alternative MRI contrasts and sequences as well that can be used along with the high energy, signal-to-noise advantaged hardware. But unfortunately, due to uncontrolled bleeding risks, liver biopsies are not an option.
The reason to make sure that the diagnosis is certain is that it allows your doctors to take on the additional risks involved with the various treatment options. If the doctors are only mildly suspicious, they'll likely be hesitant about trying the more invasive and dangerous therapies. Also, adenomas are quite rare, the annual incidence of hepatic adenoma is 1 to 1.3 per million. So they need to be sure.
You are right about the birth control pill factor. It increases the likelihood of adenomas from the 1/million rate but increases to 3.4 per 100,000 in long-term oral contraceptive pills (OCPs) and other estrogens users.
There are two primary risks with hepatic adenomas: hemorrhage and malignant transformation. HCAs are benign but on rare occasions, they will make the malignant transformation but this is very hard to detect. That's why resections make sense, in any cases that are even remotely suspicious or considered dangerous - Symptomatic tumors should be resected, regardless of size.
Hemorrhage occurred in 15.8% of all hepatocellular adenoma lesions. Rupture and intraperitoneal bleeding were reported in 17.5% of patients. The mortality rate associated with an acute hemorrhage into the peritoneum may be as high as 25-30% in patients with large tumors. In a systematic review including a total of 1176 patients, the overall frequency of hemorrhage was 27.2% among patients. Hemorrhage occurred in 15.8% of all hepatocellular adenoma lesions. Rupture and intraperitoneal bleeding were reported in 17.5% of patients.
How hepatocellular adenoma become malignant isn't well understood, and it just takes a few atypical cells to make the jump. The risk of malignant transformation is not completely known either and may be as high as 13% based on small studies. Given that OCP's are closely related tp HCA's, patients should stop using oral contraceptives or steroids. This allows for regression in the size of the majority of the tumors. Complete resolution isn't common though and the risk of malignant transformation remains even after the contraceptive or steroid use has been discontinued.
I've heard that getting a referral to a good hepatologist in the UK can be a long battle. But you need that specialist asap, so hopefully things will work out for you. Also, in addition, feel free to drop me a note if you'd like to bounce some ideas or thoughts around. I have rare issues/tumors myself so I know how lonely it can be wrt talking about things with people who have any no idea about what's really going on.
Take care and let us know how you are doing.