UK Iphone unlocked?

If you buy a Brand New Apple Device

1. Purchase Apple Products from the Apple Online Store, Apple Retail Stores, and many Apple-authorized resellers and wireless service providers.
2. If you choose "Connect to a carrier later" (Unlocked iPhone) when you buy your iPhone, you can activate your service when you receive your device.

Within the UK, many iPhone’s purchased from a Carrier are not subsidy locked - EE and O2 being two examples. iPhones purchased directly from Apple are fully unlocked and can be used with any supported carrier.

Depending upon where you intend to use your new iPhone, perhaps consider that the Cellular chipset may differ between markets. While most (if not all) iPhones will work in most countries that have 4G/LTE and 5G networks, some cellular bands might not necessarily be available to your iPhone.

iPhone - Supported 5G and LTE networks - Apple

For maximum compatibility, purchasing a device within the market that you intend to spend most time is advised. This also simplifies warranty claims should you need to call upon them.

Only if bought directly from Apple.

If purchased from a 3rd party retailer such as Carphone Warehouse, they will require activation on a U.K. carrier, and will normally lock to the first carrier used for a period of time.