Wasn't that mostly because no one would sell more modern designs to Franco?
No, in the '50s they had American F-86 Sabers, and later they got F-104s, F-4s and F-5s. They also bought French jets in the '60s.
The engine in the 109/Buchon was a British Merlin... I guess since it was indigenous produced it was cheap and could be fielded in large numbers as a ground attack platform. The 109 last saw action in 1958 in the Ifni War in Spanish West Africa.