Peter,
Thanks for taking the time to reply. In this instance, it wasn't the certs (at least, not specifically). I ended up uninstalling it all, including PHPki, then reinstalling. I did find that the version of OpenVPN I'd installed for testing the older contrib was newer than the one downloaded by the Bridge contrib when I reinstalled.
I recreated the certs from scratch (using PHPki) then applied them to the Bridge settings, downloaded the p12 file and this time it connected no problem...
I'm just about to try it on a PC (I connected successfully via Tunnelblick on OS X), but I don't foresee any issues there.
Regards,
Des