Data about patients are available from diverse sources, including those routinely collected as individuals interact with service providers, and those provided directly by individuals through surveys. Linking these data can lead to a more complete picture about the individual, to inform either care decision making or research investigations. However, post-linkage, differences in data recording systems and formats present barriers to achieving these aims. This paper describes an approach to combine linked GP records with study observations, and reports initial challenges related to semantic and syntactic interoperability issues.