The pricing here has, until now, always been done in USD ($). They are now fiddling about with regional currencies, but I would not expect that to be working properly until at least late September knowing GOG.
You do though still pay in GBP (£) when you buy from this site. It is just your bank / PayPal will do all the converting of $ -> £ for you and charge you a transaction fee.
So in a way the regional pricing may work-out to be a good thing for those buying in from outside the USA.

If you had a GOG account before and bought games via that then you can still use the installers to reinstall a game. Unlike Steam games, the ones here are DRM-free, so they can be installed on any computer you own, as often as you would like without issue.
I would suggest that you look into finding the account details you had before though, as you cannot transfer games across here. It states that in your TOS.