I want to trade in my iPhone 7 for an iPhone 12

I don't know which mini you are considering? 64/128/256GB? Depending on the storage capacity you choose the price varies.

In the US, this is how you can determine what an iPhone Mini will cost minus the trade --> Buy iPhone 12 and iPhone 12 mini - Apple

We are all users on this user to user only forum. I don't have the time to figure out what an iPhone 12 Mini 128GB will cost you in Scotland after trade. Contact Apple in Scotland.

Here's a link you can use --> Glasgow - Apple Store - Apple (UK)

See how trade-in works --> https://www.apple.com/shop/trade-in?afid=p238%7CrTo88JDV-dc_mtid_1870765e38482_pcrid_78546500880246_pgrid_1256742275320989_&cid=aos-us-kwbi-brand--slid---product-