Thanks for the response, I really appreciate you taking the time. I think the rule which is relevant to us is:
3.1.3(e) Goods and Services Outside of the App: If your app enables people to purchase physical goods or services that will be consumed outside of the app, you must use purchase methods other than in-app purchase to collect those payments, such as Apple Pay or traditional credit card entry.
so this suggests that if you are just ”enabling“ the purchase of physical goods, you should not use IAP?
For some more context about our business model: we have a few categories you can post in, all related to physical goods. For example cars, holiday homes, tickets to events, etc. When a user creates a post, we will review it, and if it is approved we will charge the user 15% of the price they have listed the item capped at £35. Tickets is an exception, where we will only charge the user when the item is sold.