I know my post is somewhat out of date now, but I do hope the system is able to alert you about this. I'm currently writing a dissertation on the Girls' Life Brigade, so I may have a few clues as to how you could research this a little further. The Girls' Brigade, just outside Oxford, won't have these records. They were held in London at 'brigade headquarters' which was destroyed by enemy action in 1941 - I understand that all minutes, membership roles and records were destroyed.
The British Library does have some information one the GLB, though I doubt it will be sufficiently specific to give membership roles for the area you're searching. All GLB (and BLB) companies had to be affiliated to a church, Sunday school or bible study group - most were linked to churches and all of the churches were Nonconformist (Wesleyan, Baptist, Methodist Congregational etc), they may well have kept the records.
Having looked at rather a lot of GLB uniforms over the last few months, I can say that you are looking at the early days of the organisation. I would suggest 1920s at the latest.
I hope this has been of some help to you. If you do discover anything further - do let me know.
