New pc needs a language that isnt in the first boot prompt

Hello, I got today a laptop for a friend, and the core condition that I said in the shop before buying it, was: the laptop needs to run in English-UK, as she’s British and can’t speak Spanish (we live in Spain). Although they said "yes no problem, just select the language at the beginning, and the system will be in that language" – it isn’t as easy, as there is not English-UK. Just català...