The public release of ChatGPT in November 2022 brought excitement and concerns regarding students' use of language models in higher education. However, little research has empirically investigated students' intention to adopt ChatGPT. This study developed a theoretical model based on the Unified Theory of Acceptance and Use of Technology (UTAUT) with an additional construct- anxiety, to investigate university students' adoption intention of ChatGPT in two higher education contexts-- the UK and Nepal. 239 and 226 questionnaires were deemed sufficient for data analysis for Nepal and the UK, respectively. We utilised the structural equation modelling technique to test the hypotheses. Our results reveal that performance expectancy, effort expectancy and social influence significantly impacted the adoption intention of ChatGPT for both countries. However, anxiety's impact varied between Nepal and the UK. Integrating UTAUT with a cross-country comparative approach provides insights into how ChatGPT's reception diverges between different higher education contexts. Our results also have implications for technology companies aiming to expand language models' availability worldwide.