Hi Juliet, in answer to your questions:
1. Yes, Vantage can be used in the UK. You set the region and currency from within the
Vantage admin dashboard.
2. Yes, you can use whatever domain name you like, and need your own host account to go with it (you can read about our
hosting promotion here). To clarify, our themes cannot be installed on the free WordPress.com blogs.
3. WordPress itself is free, however the themes and products we create here at AppThemes do need to be purchased. Our themes are designed to run on WordPress and require an instance to be installed in order to actually work. Our themes extend the functionality of WordPress to give you all the features you see on the
demo site, and there are some great examples on the
AppThemes customer showcase of the various uses and customizations which can be made to the themes to make them even more unique. You'll see it's more than just for blogging ;)
4. If you purchase by credit card or actual PayPal/Google Wallet funds, then the transaction is immediate and the theme become available right away. If you pay by eCheck then it can take 5-7 days to clear before you will receive the theme.
5. The hardest part for a complete novice would likely be setting up WordPress itself, however with hosting providers such as the ones mentioned in our WordPress hosting page, that process is made even easier with their one-click installations (i.e. the installer does all the work for you). Otherwise, you may like to view the
installation documentation for a better idea of what is involved. Ultimately though, you don't have to be a coder in order to use the theme and set up a site.
Please feel free to ask if there's anything else you're not sure of :) Thanks.