Just a possibility Ken,

Around the period you mention, the Drill Hall in Peel Road, Douglas, may well have been the centre for enlistment. The building has had various functions since then and at one time, and still possibly, was a depot for grading and preparing Manx wool for export.

A further Drill Hall which superceded the previous building was erected, probably just prior to the last war around 1938 on the outskirts of Douglas at Tromode. This now houses the Isle of Man Water Board but I believe part of it is assigned for use by the Museum and possibly the Archives of the Manx Regiment in World War two.