I should stop this thinking lark

Here's what I've been thinking about today:

 

Out of all the male humans in the United Kingdom are there more that have the first name John, or more that have the initials JS (ignoring middle names)?

 

I'm really not sure. There are a lot of people called John to be sure, with all sorts of surnames (eg John Prescott). But there are also a lot of people with the initials JS (eg Jackie Stewart). There are also many people called John with a surname beginning with S (eg John Smith) who would score a tick in both categories.

 

Now, this isn't a life or death matter but it would be nice to have a definitive answer.