This is all obviously very subjective of course, but I do question the relative usefulness of Spanish (I say this as a near-fluent speaker, who has been employed for my Spanish skills in the past).
It is true that Spanish is the second most spoken language as a first language, but the majority of those speakers live in Latin America. Countries which the UK generally does not have much trade with, and a part of the world in which we have relatively limited influence. That's not to say that Spanish isn't useful, or doesn't deserve to be in the top 10, but the argument that it is spoken by x million speakers in 4 continents isn't really the most supportive one.
I wish I'd put more effort into learning Portuguese than Spanish- purely for the growing importance of Brazil (as well as an interest in Lusophone Africa).
Similarly, to those who question why Hindi isn't on the list- India is obviously an important trading partner, but India does business with the world in English. Furthermore, in non-Hindi speaking cities (which include important commercial centres such as Mumbai, Calcutta, Bangalore, Hyderabad etc.) there can be reluctance to speak Hindi. Again, that's not to say that learning Hindi couldn't be worthwhile or give some advantage in the jobs market, but it is not an essential or even highly sought after requirement for doing business with India.