Welcome to the forum.
If the deceased is a direct descendent then you can apply for his service records, or the NoK can. Most medal cards for WW2 haven't been released yet (except gallentry awards), and the only way of knowing is through his records.
Service records - Army
May I ask how you know that he was beheaded. His date of death precedes the surrender of Singapore? And the Sherwoods had only arrived a week before his death.