Very, very nice, as complete uniforms are a rarity. Looking at the medal ribbon, your Lieut appears to belong to a Territorial Army battalion, as it looks to be the Territorial Medal, rather than a campaign medal, but he should still appear in the R.N.F. section of the Army List for the what I would believe would be the post-World WarII period, but sadly Brown isn't an uncommon name.
When I have time I'll look through my regimental journals to see if he makes and appearance.