Hmm. Google and transparency. Not words you see in a sentence very often
And usually in a poorer light than this.
Yes strong contracts and penalty clauses (and enforcing penalty clauses) will help.
Google is a data fetishist with a high recidivism rate (like other kinds of socially unacceptable fetishists).
IOW They can no more keep their hands off patients data (and it's patients data, not the NHS's to sell or give away) than Uncle Ernie can keep his hands off Tommy (Nice work by Phil Collins, really channeling his inner nonce).