Hi
Always use a currency broker if transferring large amounts. Don't transfer large amounts via your own bank as you won't get the best exchange rate.
I've used Caxton FX for years. I think they are brilliant and if they feel you should wait until X date to get a better rate and you can wait they will tell you. You can also ask them to track the market for you to see if you can get a higher rate.
Also they do not charge transfer fees to transfer into your Spanish account.