I wouldn't think it would be a very usual occurence. The British nobility mostly married members of other British noble families. Apart from anything else, most Spaniards were Catholics, and most British people at this time were Protestants and very anti-catholic.
However, I suppose it is possible that a British nobleman travelling in Spain for some reason might meet a Spanish noblewoman and fall in love with her. If he wanted to marry a Spanish woman whether his family had any say in the matter would depend on his age, whether he held a title in his own right etc. If, say, he was an Earl or a Baron, nobody could stop him marrying whoever he liked. if he was only the son of a nobleman then his father would expect to have some say in whom his son married, and could make difficulties if he didn't approve of the match.
There would also be the Spanish noblewoman's family to consider. Young unmarried Spanish women of good family were normally chaperoned, and would not be allowed to meet anyone their family considered unsuitable. Whether a Spanish nobleman would want his daughter marrying an heretical englishman is doubtful.