Background Children and young people (CYP) from underrepresented communities in the Liverpool and Sefton regions (UK) experienced an increase in mental health needs, pre-pandemic. The “CYP as One” online platform was introduced via a co-creation schedule, to support the uptake of service users into child and adolescent mental health services. However, post-pandemic, the risk of poor mental health for CYP further increased. The current study co-customised the “CYP as One” platform to facilitate the wider access and inclusion of CYP from underserved communities into relevant mental health services through ensuring their viewpoints are sufficiently represented in the referral process. Methods The co-customisation schedule utilised the Living lab approach. Service user feedback was extracted from the “CYP as One” platform and data was generated via seven online focus groups conducted over two months. The focus groups included 16-19-year-old young people; parents of under 16-year-old children and health service providers. Content analysis was conducted on service user feedback, which was covertly presented to focus group participants to aid the conversations during the focus groups. The final data analysis involved conducting a thematic analysis on service user feedback and focus group data. Findings The thematic analysis on service user feedback and focus group data returned seven themes. Contrasting preferences of referral methods; the importance of inclusive access to a wide range of platform users; the relevance of demonstrating empathy and sympathy via non-face-to-face referrals; perspective taking aids in the mutual understanding of the needs of stakeholders involved; digital content should account for age and social-development related differences in this context; CYP and parents require timely and relevant mental health information; digital means of referral methods may integrate fragmented services. Conclusions Involving insights from service users; the public and health service providers allowed the in-depth exploration of everyday challenges service users may face when using the “CYP as One” platform. The solutions identified by participants to such issues represent a reliable improvement to the platform. Ensuring that the digital content can replace in-person referral processes is of utmost importance to support CYP who previously experienced difficulties in engaging with mental health services.