Every situation is unique and the Spanish are even better than the Germans/Swedes when it comes to inventing bureaucracy, im sure your trying to be the good European but wouldn`t it be simpler to trade over your UK bank and send something every month to cover your Spanish costs!
With regards to tax in general,their are plenty of Loopholes in Spain if you establish your own company and work around that!,if you need a local tax lawyer feel free to PM me and i will send you some contact details !