As Billg says, bank cheque (cheque bancario) costs are negotiable. It’s very important to nail this down when you open an account, as otherwise banks can really sting you for this.
To give you a comparison, I paid €60 for a bank cheque from La Caixa last year, cheque amount was around €300,000. I didn’t have to negotiate this as the condition was included in my type of account.
I use La Caxia for my banking needs and am happy with them. They have a brand for foreigners in Spain called HolaBank, you can find out more here: https://portal.lacaixa.es/holabank/particulares_en.html
When it comes to transferring money from abroad, don’t use your highstreet bank if you also need currency exchange, for example changing Pounds into Euro. You get a much better rate from a specialist foreign exchange broker. If you are comfortable with technology, and don’t mind doing the buy/sell yourself, then I use http://currencyfair.com/ for the very best rates.
If, on the other hand, you want some advice from a currency broker, and someone to help you with the purchase, then there are several specialist forex companies to choose from. For example Torfx (see the ad in the column to the right). If you buy through them I get a commission, which all helps to keep this site running ;-).
Where in Spain are you buying, if you don’t mind me asking?