COVID-19 restrictions significantly impacted the operations of fast food and full-service retailers. Full-service retailers were permitted to operate as takeaway outlets without needing to seek formal changes in planning permissions. We conducted a study to determine consumers' intake and modes of accessing foods from fast food and full-service retailers during various COVID-19 restrictions and changes to takeaway/delivery regulations, as well as their experiences. We conducted a longitudinal, mixed-methods study comprising three surveys, which examined the intake frequency and modes of accessing retailers, and two rounds of qualitative focus groups, which explored their related experiences. The data were collected at three timepoints (T) from May 2021-March 2022. The participants were adults living in Northern England (n = 701 at T1); a sub-sample participated in the focus groups (n = 22). The intake data were presented descriptively; an ordered logit regression explored the factors associated with the intake frequency. The focus group data were analysed using a framework analysis. The mean weekly intake frequency from fast food retailers at T1, T2, and T3 was 0.96 (SD 1.05), 1.08 (SD 1.16), and 1.06 times (SD 1.12), respectively. For full-service retailers, this was 0.36 (SD 0.69), 0.75 (1.06), and 0.71 (SD 0.99) times, respectively. Food access issues (OR (SE): T1 = 1.65 (0.40), T2 = 2.60 (0.66), T = 2.1 (0.62)) and obesity (T1 = 1.61 (0.31), T2 = 2.21 (0.46), T3 = 1.85 (0.42)) were positively associated with intake from fast food, but not full-service retailers. Delivery services were commonly used to access fast food (30-34% participants), but not full-service retailers (6-10% participants). As COVID-19 restrictions eased, participants were eager to socialise on-premises at full-service retailers. Takeaway/delivery services were seldom used to access full-service retailers, but the use of delivery services to access fast food was high. Policymakers must recognise delivery services as a growing part of the food environment, and the challenges they pose to planning policies for obesity prevention.