In the last years I helped spanish colleagues to get jobs in London.
I learned that the main challenge to get a job in London it is not the language. In england the two things that matter the most are (1)experience and (2)references. Unfortunately the long engineering degrees in Spain do not give you either of the two.
So, I recommend if you consider moving to London, (1)have a good proof of your work done and (2)explore your network to find relevant people already working in the city that could introduce you to employers.
This is the slide deck of a presentation I gave in the Polytechnic University of Valencia with detail information for software developers who want to find a tech job in London.
