This reads like GCHQ was the naughty kid, not paying attention, and they took pity on them when they asked for help ... but at least they asked. But to rub it in they did a "the solution is left as an exercise for the reader" deal. Kinda hilarious.
That said, you could spin it another way: the UK had enough good will and political capital to lean on its European neighbors for a bare-minimum amount of help. "We can tell you how it works, but it's on you to figure the rest out".
Naughty kid not paying attention is also relevant -- you've only got so many hours in the day and so many hours to map out threats. This was still the Cold War and nuclear holocaust was a bigger priority than distant Latin American dictatorship.