You also have a long period of time to work on your credit rating between now and when you will have to submit an application to BBVA. There is a massive amount to get through between now and then as well. I would suggest you sign up to Experian and get your credit score/rating. You will learn a lot just from this. Then use the tools that Experian membership gives you to improve your rating over the next 9 months or so.
At the moment you dont know what you dont know... So if Credit Rating is worrying you find out what it is... you might be surprised.