We'd like to make this more clear.
Hyperoptic assigns the IP to every customer and each IP is located in UK. We did add a new range of IPs to the pool from which we assign IPs to the customers. This new range of IPs was in the past registered to different locations than UK, however, they have been purchased from UK regulatory body as a UK registered IP address.
Every IP can be found in global Geolocation database. The issue is, if someone (the website you were visiting) is using an old geolocation database, it may show as your location to be outside of UK.
This is resolved by them (the website) updating their geolocation database as it's out of date. We are not the only provider that has this issue or had this issue in the past.
As the IP ranges are bought and sold from providers who no longer work.
The solution for this problem is contacting the service you are trying to use and asking them to update their geolocation database. We will do the same from our side.