The Volunteer Training Corps was the First World War equivalent of the Home Guard.

No personal service records are known to exist, and medal records will not be able to help, as no campaign medal was given for home service (although if an individual had previous or later service abroad he would have been eligible).

Officers are listed in the Volunteer Force List, and we have issues of this from October 1917 and October 1918. 

You may find some material held locally or with the relevant regiments.

The Imperial War Museum's Department of Printed Books has the following as well as a few unit histories:

The Volunteer Force and the Volunteer Training Corps during the Great War: official record of the Central Association Volunteer Regiments - London: P.S. King, 1920. - vi, 63p.; 19cm.

The official regulations for Volunteer Training Corps and for County Volunteer
organisations (England and Wales) / edited by J.P. Blake. - London: Central
Association Volunteer Training Corps, 1916. - 128p.: ill.; 19cm.

Official regulations for Volunteer Training Corps and for County Volunteer
orgainsations (England and Wales) / edited by J.P. Blake. - London: Central
Association Volunteer Training Corps, 1915. - 104p.: ill.; 19cm. - index.

The Volunteer Training Corps Gazette  [December 1914-September 1917]