Whoa Ewick...deep breath...

I don't know what websites you've been looking at but -- in my experience -- ALL spanish rating are based on the french system. In other words, the info you have (F4 or whatever) is wrong. (Though, El Chorro IS in Andalucia and if they grade climbs like they pronouce Castillan, things COULD be a little different). Here's what you can expect:
5+ = .9/.10a
6a = .10b
6a+ = .10c
6b = .10d
6b+ = .11a
6c = .11b
6c+ = .11c
7a = .11d
7a+ = .12a
7b = .12b
7b+ = .12c
7c = .12d
7c+ = .13a
8a = .13b
etc etc...now that you know the pattern...
9a = .14d
and the hardest proposed route in Spain is...I believe...
9b+ or .15c
I can't speak with any authority on the lower grades, 5.9 and below, as where I climbed (Cuenca, Spain) there were no routes below 6a and few below 7a. Also, while the french to american translation isn't completely exact, I encountered no problems and the aforementioned schema worked great once I got the hang of it. In general, though, the lower grades below 7a were, as I found it, more variable than higher ones.
Hope this helps amigo...