Hehe that's funny! When are you heading down there? Torres del Paine I guess?
You're right it is only £5 but I am a cheapskate
I have been able to select the seats without choosing to go to payment and they seem to be saved if I exit and go back in so I don't know if that means they are reserved or not. Weird. We flew some domestic flights last year in Peru with LATAM and didn't have any issue selecting seats for free so not sure why it isn't working now.