Assuming the English Will is not expressly restricted to English assets, it should also cover Spanish assets.
Assuming the deceased is English, Spain should accept the will as Art 27(1)(b) of the Directive provides that a will "shall be valid as to its form" provided it complies with the law of nationality of the deceased.
Assuming the deceased was habitually resident in England, the substance and devolution would be subject to English law as well under the general rule in Art 21. If not, but the will makes reference to English statutes you can argue that an election was made under Art 22(2) ("demonstrated by the terms of such a disposition") and then the substance of the will would also be governed by English law (Art 24(2)).
If not, you would need to look at the country of habitual residence and Spanish law in more detail.
Osborne Clarke LLP