Underage soldier joining Worcesters

[Willis]

I am doing some family history research into a soldier who enlisted in Coventry into the Worcestershire Regiment in March 1916, aged 16, clearly under age for active service. In a time before birth certificates, he must have lied about his age, as many soldiers did. He must have been some fellow, rising to the rank of Sergeant at the age of 18 (even if the Army thought he was 20+).

27616 Harold Bertram "Berty" Bloor

He served with the BEF in F&F from 16th April 1917. He later transferred to the 34th Battalion the Machine Gun Corp and was wounded in France around the 1st of August 1918. He died of his wounds on 11th August at the hospital in Rouen and is buried there.

How would he have been allocated to the Worcestershire Regiment?

I have no information on him between the dates he enlisted in March 1916 and his transfer to the MGC (his Service Number there was 55071) in February 1918, when the 34th MGC was formed. Can anyone fill in any blanks?