Congrats on these offers - and scholarships!  This is not an easy decision in light of the differences in location, cost, duration, and differing work visa policies - not to mention how each of these factors line up with your personal situation and career goals.

While it sounds like you have your post-MBA goals sorted in terms of geography (Spain), the task of choosing a school might be easier if you also had a sense of the industry of function you are most likely to target post-MBA - since each school has strengths in certain domains.  Understanding your career plans could point the way in terms of program format (e.g. if you are career switching, it can be helpful to be in a two year program). 

Many would argue that LBS > IESE > Oxford if you are talking purely about historical MBA rankings.  Of course, if landing in Spain is goal #1, IESE clearly has an advantage.  Similarly, if you are looking for a speedy, low-cost path to an MBA, Oxford earns points in light of their 1-year format and generous scholarship offer.  Then again, if you think the job market in London - and the breadth of strengths LBS has academically and in terms of network scope - is appealing, you can make the argument that it's the safe bet.  

I should also mention that as a non-European, it might behoove you to look into visa policies - as they vary quite a bit between the EU and the UK.  For instance, earning your MBA at LBS or Oxford gives you automatic eligibility to work for two years in the UK following graduation - without the need of an employer sponsor.  In Spain, you can apply for a 1-year visa that allows you to stay in-country after graduation to look for employment, but once you have an offer, you and your employer would need to apply for a residence and work permit, which requires paperwork and isn't guaranteed.

In short, there are a lot of factors here, and it's not an obvious choice.  I would recommend that you speak with career services at each institution and get an honest take on your options.  You should also attend any welcome events for admitted students to gauge the caliber of your future classmates and see the schools up close.  Best of luck!