My personal preference would have been London, as It would have been easy to organise for me, as I could have organised a trendy pub and got us in VIP to good club.
In respect of dates, you can never please everyone, and if you really wanted to attend the event then its down to the individual to either take the Friday off, or just join on Saturday. Not sure a lot of people could make it on a bank holiday weekend, when hotel prices, flights etc will be inflated.
The venue was picked because it is on the south side of Birmingham, easy access from the airport, and easy access from the south.
As you obviously have the knowledge of Birmingham, I am happy to stand down and let you organise things. I will cancel the proposed meet up, and perhaps you can organise a new event........whatever dates you think, organise a pub for the quiz, post some reasonable priced hotels etc (just remember not all people want to go out in central Birmingham, in all the piss, sweat and puke.... to have a drink)