Hi Inigo.
Thanks for the awesome plugin, i love TCP and i even had QuickPay make a plug-and-play payment gate for your plugin, you can find it here if u want to add it to your website: https://www.ads-software.com/plugins/thecartpress-quickpay-payment-gateway/
Regarding to taxes. i have added a Tax of 25% called “moms” which is the name in Denmark. after that i added a new product and gave it “moms” in product setup tab of the product, but when i view the product, it shows only the product price, no taxes.. i can live with that, but the problem is that it does not show anything in the shopping cart page either, it just shows the product price, subtotal and total which are the same ones since no tax are calculated .. i hope you understand what i mean.