So if you use a VPN such as Hola, you can purchase Overwatch for around 16.50 GDP.
All you have to do is go to:https://tw.battle.net/shop/en/product/overwatch
Turn the VPN on and go to Taiwan, VPN may not even be needed. Go through to payment and select your payment method, most like Paypal. Turn VPN off before logging into Paypal and then go through and purchase your game.
Very cheap method to get Overwatch, installs and plays in English (UK).