There is no known company currently trading under the name "Supermarket Co UK." A search of UK company registers (Companies House), trademark databases, and retail directories yields no active entity with that exact name.
Therefore, it does not operate in the UK or abroad. If you encountered this name in a specific context (e.g., a fictional scenario, a dissolved company, or a typo for a real chain like "Supermarket Co." or "UK Supermarket"), please provide additional details for a more precise answer.