Does anyone now of an Magento plug in which allows a product in a customer basket to be upgraded and switched by customer?
For example, customer buys a coin in the webshop and proceeds to basket. Basket offer - choose the special gold edition for just £10 more. if customer chooses Yes, gold version goes into basket - original version comes out.
"Product Upsell" by Amasty: This extension enables you to set up product upgrades, cross-sells, and upsells in the shopping cart. It allows you to create upgrade options for customers and offers them the opportunity to switch to a higher-priced or alternative product.
"Product Options by MageWorx" (formerly known as "Custom Product Options"): This extension lets you create customizable product options, including upgrade options. You can configure pricing, conditions, and rules to offer customers the ability to switch or upgrade their products in the shopping cart.
"Advanced Product Options" by Mageworx: This extension offers advanced product options, including the ability to create custom product bundles and upgrade options. Customers can choose to upgrade their products and see the price difference in real-time.
"Product Options Suite" by Amasty: This extension allows you to create product options and upgrade options for your products. Customers can select different product variations or upgrade options directly in the shopping cart.
These are some of the related extensions I shared, if that doesn't fulfill your requirement, I would suggest to get the custom develop according to your requirements.