I am sorry to hear that things didn't work out for you.
My understanding is that closing a company is difficult and will incur costs. Some of my friends are still trying to do it after more than 2 years and they keep get told that they have to pay a few thousand towards stuff they don't even know about.
Anyway, there is another option in Spain which is where you can officially suspend trading on an SL, in other words you put the company in "sleep" mode. I'm not exactly sure how it's done but it is possible. Then all you need to do is once a year submit a form to show zero earnings. I think it's difinitely the cheapest and easiest option for you.
Maybe Maria, the lawyer on the forum here, can give you some pointers as to how to go about it.
Best of luck with it.
Justin