Lucky you! I love Barcelona, wouldn't mind moving there...
I think your best bet is to find a local shop that has a digital minilab (Look for Fuji Frontier, Fuji FDI or Kodak/Noritsu).
I'm sure there must be some in Barcelona.
I thought about using an online service, but uploading through internet takes ages...
I found a local shop with a Fuji Frontier: fast, cheap, truly amazing quality and I just drop of a CDR with my pictures.
It doesn't need to be 'pro' service lab either.
You can instruct these machines to print without any corrections, so you can have total control yourself. All pictures come out exactly as I intended.
I pay 30 eurocents for a 10cm x 15cm print