The bird is pretty good - certainly Iberian-derived, and the frequency, length and three-phase nature of the song are pretty good. The verbal description of the song in post 6 are spot on for Iberian, but in the YouTube videos the song is quite low intensity and in fact several of the songs are pretty messed up for Iberian and combine classic Iberian 'wheeps (the upward strophes) with notes that, while not ruling Iberian out, are more characteristic of Common Chiffie. It's borderline, but I am erring on the side of mixed singing, and therefore potentially with hybrid influence. In the photos, the bird has quite a long primary projection, very yellowy fore-super, and brownish legs, that are good for Iberian. The eye ring is quite weak, good for Iberian, but classically it would be more obvious below the eye than above, whereas this bird looks even above and below. Physically the bird looks OK for Iberian. Song-wise, it is not totally classic on the videos, though it may produce better songs as per the description.
Anyway, here are some sonograms taken from you Tube.
And this is the paper I did with Tim Melling
Collinson JM, Melling T. 2008. Identification of vagrant Iberian Chiffchaffs - pointers, pitfalls and problem birds. Brit Birds 101, 174-188.
I can provide pdfs of that