Purchasing the iPhone 15 Pro in the UK

Keep in mind that Millions upon Millions around the world preordered an iPhone for delivery or pickup at an Apple Store on the 22nd. While Apple "sometimes" has some very limited stock available for walk-in customers, you'd need to get in line outside your Apple Store hours before it opens and be prepared to find they don't have the model, color or storage option you want available. And your Apple Store will be jammed with long lines of people who have preordered.

You can still preorder today, but there's pretty much a ZERO percent chance of getting one by preorder for delivery tomorrow.

Starting tomorrow, you can just order one (it will no longer be considered preordering as the phone launches officially tomorrow. But whenever you order, expects some delays as some models are sold out into October and some into November.

In the UK Friday 22/9.

Both. But supplies might be tight on launch day (or thereafter), and it could be that they have no phones in stock when you walk in. Best to go early in the day.