Wrong apple pen

I'm afraid, personalized items bought from Apple can't be exchanged.

However, you might be able to get a refund:

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Exchange an item

If you purchased your item from Apple in the U.S., you can take it to any U.S. Apple Store for an exchange. Item exchanges are, of course, subject to in-store product availability. It's a good idea to check if a product is in stock by visiting apple.com and then seeing if it's available for pickup at a store nearby. The only exchange exceptions are personalized items (such as engraved iPad or AirPods) and Macs that have been custom-configured. These items cannot be exchanged in store; they can only be returned and your refund will be issued to the payment method you used on your order (per the guidelines in our Standard Return Policy).

Items ordered online from Apple that arrived damaged or are incorrect can be returned to any U.S. Apple Store, or by contacting Customer Service at 1-800-676-2775.

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copied from: Returns & Refunds - Shopping Help - Apple

You could return it back from where you bought it from, buy an iPad that supports the 2nd Generation Apple Pencil or sell your pencil.

You're welcome 🙂

Glad you were able to return it without any problems due to the different return policy in the UK.