For orders delivered to the UK, the price you have seen in the checkout is the total you will pay delivered.
Outside the United Kingdom
If you live OUTSIDE, the UK then the 20% UK sales tax will have been removed automatically and you may be liable for duties and taxes on import/arrival.
All the carriers operate in slightly different ways, but they will all deal with customs on your behalf. Some will contact you before delivery, some after. Sometimes it will be the carrier and other times it will be customs themselves. It is worth noting that there is normally charge a small admin fee for processing the customs paperwork.
Here is a graphic representation of the process for how orders are handled.
Here are some useful links to the main couriers that we use, you will find more information on how they operate.