We arranged our power of attorney through the Spanish Consulate in Edinburgh. A telephone call and email was all that was required then we turned up at a prebooked appointment, sat down and listened to the agreement in pigeon English, signed the document and then left with the power of attorney stamped with the seal to make it legal.
A relatively painless task and it was a lot more organised than trying to do it in Spain. The lady who helped us at the consulate asked us about NIE and then gave us the forms to complete. She said they would then process them in 6-8 weeks. We are not in a hurry so this arrangement was very relaxed, again it seemed to be less stressful than those who have applied in Spain. The numbers will be posted out to us when ready. We already have a Spanish bank account but having the NIE just now will save time when we come to arrange the mortgage.
The consulate is a short walk from Waverly train station and is easy to spot with the Spanish flag flying out side the buiding.