Will iPhone 11 A2223 work in the U.K?

The A2223 iPhone 11 is not compatible with any UK networks. It isn't compatible with any networks outside of Hong Kong, China and Macao, either: iPhone- View countries with supported LTE networks

The link I have provided is from Apple. It states what countries the phone can be used in and the carriers/networks it can be used with.

The Apple employee may have confused the A2223 model with the A2221 model, which is compatible with the major networks (such as O2, 3, EE and Vodafone) as well as some less known ones (such as Sky and Virgin Mobile).