Dear 2shea,
I can't comment on the marriage situation, but the bandmaster bit is interesting. Suggest you check his title on the music, whether its really Militia, Monmouthshire Light Infantry, Monmouthshire Regiment etc - picky I know but....
If he's living in St Mary Street, Monmouth, and was bandmaster to the
Royal Monmouth anything, chances are it was the local Militia pre 1857, what is now the RMRE - allegedly the only unit with a double Royal in the title these days. Seeing as your boy is in Southwark in 1851, its unlikely he'd be tied in to a Monmouthshire military unit before that
http://www.monmouthcastlemuseum.org.uk/militia.htmIf it was the Monmouthshire Regiment (or one of the other units who formed the South Wales Borderers), you may need to look at
http://www.rrw.org.uk/There is probably a lot of Grenadier Guard Band information out there
perhaps a good contact would be
http://www.grenadierguardsassn.freeserve.co.uk/ggaassoc.htmrhqgrengds@yahoo.co.ukYou may be able to find a Victorian Military website, or something like Soldiers of the Queen (c.f. Rootschat or the Great War Forum) but I don't know of one.
http://www.vms.org.uk/fpage.htmlHope this helps,
Simon