Tell you what, I'll put all the panniers and Ventura kit back on my ST and you can take that to Spain.
I'll look after your SP4 for you
Seriously though, have you thought about using one of those tour companies that will take your stuff to a given hotel or B&B every day in a support van like Sparkin said. There was a guy on this board who ran stuff like that in Spain(bought a Corbin saddle off him but cant remember his name), they haul your stuff round to known points, you just blat off and do your own thing between brekkie and dinner and your stuff is waiting for you at the other end.