Although it is well known that there are financial limitations on U.K. National Health Service treatment for severe obesity, little is known about how these constraints affect decision-making in clinic. In this study, we combined two qualitative methods (non-participant observation and in-depth interviews) to examine decision-making in progress. A longitudinal approach was taken to research and patients were followed up for up to 3 years. In total, 22 consultations were observed and 78 in-depth interviews were undertaken. Participants were sampled purposefully, and data were analyzed using a combination of narrative and thematic approaches. We met a number of practical challenges during the research, including how to undertake purposeful sampling while respecting patient confidentiality, how to ensure consultation-recordings were undertaken reliably while the researcher was not on-site, and how to go about synthesizing data from the two different methodologies used. A number of additional challenges arose, including gaining the trust of clinicians who were uncomfortable when discussing the impact of financial limitations on treatment decision-making and how to initiate and maintain long-term relationships with patients, many of whom had had poor experiences of accessing health care in the past.