Ayup ben, this used to be my old stomping ground… So have a few suggestions (moved to Oz 4 years ago so worth checking them online to see if they are still good…)
The goldsmith on southward bridge rd (between southwark and borough tube stations)- we hired the whole pub for our leaving do (i think it was just a minimum spend at the bar), we had free reign of music (plugged our ipod in) and they catered also. Was a great time and they used to have cracking beer too..
The roebuck on great dover street (near borough tube station) has a few seats outside (although you can’t book them), a private function room upstairs and fairly decent food. Beer used to be pretty good there – mostly craft beer and lagers… This used to be our local and is a really nice, friendly pub and is pretty big.
The old red lion on kennington lane (near kennington tube) – bit of a walk but a great pub and you used to be able to book out the conservatory bit out the back for a minimum spend (we had our engagement party). They sometimes have a weird beer selection to compliment their standard taps…
The laughing gravy on southward bridge rd (Southwark Tube Station) – great food but a bit pricey, more gastropub than boozer.
The royal oak on tabard street – routinely wins best pub ever from CAMRA (London bridge or Borough). Properly great old school boozer, traditional pub grub, not the biggest and used to have stinky toilets. Byut they do harveys beer and they do it really, really well.
We are moving back in a few weeks so will give you an update on whether they are still as good!