would appreciate suggestions rather than opinions>>

my suggestion is that you stay in Spain and spend more time in the places you have mentioned.

Kimhe as ever has more excellent suggestions too.

OK, if you don't want to stay in Spain, then I would vote for London - I live here and LOVE it! There is so much to see.
" .. when a man is tired of London, he is tired of life; for there is in London all that life can afford" Samuel Johnson

kinhe: I love your recommendations - thank you. I spent too short a time in San Sebastian, and need to go back :). As I was driving through the region, I was listening to The Basque History of the World - such a great book!