Hi @grahamfern, thank you for supporting us by subscribing to Windy Premium!
To access your premium features, follow steps in this manual: https://community.windy.com/topic/11832/what-to-do-if-you-can-t-access-your-windy-premium-features.
Note that the restoration process has to be followed on the device you originally placed an order.
Once you have Premium features available on your iOS device, log in to your browser and you should see it there as well.