Hi,
1. Normally, you should ask this question to your tax office as tax rules are complex and differ widely from one country to the other and depending on what you're selling. however, usually, when someone purchase a shippable good, you should tax it based on the delivery address. So in your example, the UK tax rate should apply. In the Hikashop configuration, you have the setting "Type of address used for tax" to select if the system should base itself on the billing address or the shipping address for tax calculations.
2. Yes. Note that by default, HikaShop will use the billing address for the "zone" restriction of payment methods.
So in your example, the payment method won't be available to the US customer as his billing address is in the USA. There are two ways to allow for that:
- You can restrict the zone on the shipping methods instead of the payment method. That way, it will be based on the shipping address automatically.
- You can go in your PHPMyAdmin and add an entry in the hikashop_config table with the namekey payment_methods_zone_address_type and the value shipping_address
That way, the zone restriction on the payment methods will be based off the shipping address
Regarding the currency, it's easy. Just publish the GBP currency and keep the other currencies unpublished and the payment will happen in GBP. The bank of the customer will automatically convert the amount when removing the money from his bank account (with usually a small fee for him).