I think an issue could be that while Kane prefers England, his desire might not be as strong as Levy's is to avoid selling within the PL. Kane would probably not take so much convincing by a club of Real Madrid's dimensions.
Whereas I think we'd have to do (or pay) a heck of a lot to persuade Levy, something people continually underestimate when they talk about Levy cash grabbing and being a businessman so therefore he'll panic because Harry's got a year left. Not a chance.
I think if this ever got to a free transfer we'd have had a great chance, but the transfer looks very difficult. Which in all honesty I don't think is such a bad thing for us. I hope it might focus our mind early in the window for alternatives and getting on with strengthening the wider squad, something that will be frustrated by a summer long Kane negotiation.