HI, re getting a mortgage, I believe mortgages are assured by Banc Pastor as the funding bank for the development but this is only what friends told me and so it is maybe best to chat to your solicitor who I am sure can recommend a bank they work with.
If not, you could do worse than talking directly with the Halifax in Fuengirolla - I have met them a couple of times and they are very helpful and have English speaking staff if your spanish is not great. Also try Barclays Spain, they advertised the lowest interest rates earlier this year. You do not need to pay a broker to help you with this, they can charge more than €500 - the banks here will help you in English and it may be worth you investing in a quick trip out here to meet with Halifax and Barclays locally to chat through your needs.
Good luck.