IIRC, some universities, such as Warwick, offer the option to spend a year abroad studying a non-UK legal system in English, but AFAIK most degrees in law plus the law of (a non-UK jurisdiction) require a high level of ability in the language of the non-UK jurisdiction, and the year (or more) abroad is spent at a university in that jurisdiction, being taught in the local language.
My nephew started at Oxford doing Jurisprudence, but his French was good enough for him to switch to Law with French law and spend a year studying in Paris. Before doing so, he had to satisfy the Fellow and Tutor in French at his college and a French lawyer who is a Fellow of another college that his (my nephew's) French was of a sufficient standard.
If you haven't studied Spanish to A Level or IB higher level, you could maybe take some external courses to get your Spanish up to the requisite standard. My daughter starts Jurisprudence at Oxford in October and is currently working on her French (she has IB French at lower level), and taking an exam in French next month. This is to give her the chance of studying French law at undergraduate or graduate level and/or of obtaining a stage at the ECJ or the European Commission or the ECtHR (she has an EU passport) after she graduates.