Hi UXB
Hispano had built quite a few versions of the 109 already - if you watch the film about Hans Joachim Marseille (Star of Africa 1957) they used Hispano - Suiza engined HA 1112's - which were a fair representation (shape wise) of a 109F.The Merlin engined Buchon came about because of the easy availability of Merlins and Props in the post war years.
Spain was a bit isolated from the international community at that time so just had to use what was available and 'good enough' for the time.