Think again.
The opt out is so buried you probably didn't particularly notice it. If you go here:
And then read this:
Then maybe you'll take a different view to how your (only partially) anonymised medical data will travel. I for one, don't want any commercial firm gaining access to my Medical data tagged by gender, DOB and Postcode. That's enough to pin me down? How many people in your postcode share your age? Let alone your birthday?
I'm opting out, I think you should consider it carefully too.