Follow the (under construction) Metro tracks past Ian Allan's, The Royal Mail Post Office Vaults** is less than a minute away on your right. Some parts can be a bit 'musty' but the beer's quality.
I don't think anyone's mentioned Mikes Models in Kingstanding yet, as it's worth a visit (no connection etc). Obviously that's not going to be viable for New St Traincrew on PNB's etc though!
Actually, post- 14th/24th* September, Birmingham (laughingly considered as the 'second city') city centre will now be worth visiting for some real ale pubs, a beautiful station (Moor St), and er, well, that's yer lot.
* Take your pick, I've been quoted both dates for closure
** Credit to Keith (Melmerby), as I'd forgotten the current name
[EDIT - typo/syntax/senility]