Hello DE199, you're correct that Hector Hawton's real name is John Sylvester. He wrote romantic serials for British newspapers, the Daily Mirror, Daily Star and Daily Herald, pre WW2. He also wrote for Thriller. As for Chums, you might want to take a look at this site:-
http://blog.crystal-knights.co.uk/2009/01/17/chums-19067-and-19323/Still trying to tie the 2 bits up but you've got me curious.
Modifying this to admit to a senior moment - lost concentration and got the names wrong way round. So, confirming that Hector Hawton is the real name and John Sylvester is the pen name.
It also occurs to me that you might want to post the query on comicsuk:-
http://www.comicsuk.co.uk/Forum/index.phpI've made the huge assumption that you're not already aware of comicsuk or you could be a member. If so, apologies.
Another link:-
http://john-adcock.blogspot.co.uk/2010/11/chums.htmlOnly had a quick scan but can't see either name there.