I have just completed my first Spanish tax return, using a qualified tax consultant and was delighted with the result.
Although every case is different, I was advised that I had the benefit of a personal allowance for me,my wife and my child. Additionally, we had an allowance for mortgage interest.
The net result was a nil charge for tax!!! Definitely a lot less than I would have paid in the UK on my total income which I calculate would be about ?2000.
I know where I sit on the Spanish tax vs UK tax discussion.