8am (or just before, say 7.45am). Why?
These are usually 8am-8pm (or 10pm), 7 days a week. They are staffed by experienced GPs (or equivalents) and nurses.
It’s the quiet-ish time of day in a UTC or MIU [“Please don’t tell anyone”. We won’t, promise, CKDEx Ed”].
The nurses will start at 7.30-7.45am getting the UTC or MIU prepared for the day. Their mental skills are often best early in the day.
The morning shift usually starts at 8am. Again doctors mental skills will be better, and they may be more likely to get the diagnosis and treatment right. And if you arrive at 8am, and investigations are required, they will be back for the doctors to review before their shift ends. This will give you better continuity.
We have described what is the best time to go to an Urgent Treatment Centre (UTC) or Minor Illness/Injury Unit (MIU). We hope it has been helpful.