Joan Birbe is pretty easy to contact in my experience, as is Alfaro. Both located in Barcelona.
Raffaini was also easy to contact, one of his receptionists speaks pretty good English
Zarrinbal was a bit tricky but I managed to actually speak to him over the phone to book my consult, this was back in 2016 though. Perhaps have a German interpreter to contact their clinic (or a German friend), should be fairly easy that way. Shame his receptionist speaks super basic english, don't know why he hasnt changed that.
Defrancq is quick to respond to emails