Hi Hazypea and welcome to the Vine!
Sorry to hear that you've found B'ham council less than helpful - when I phoned for info they were ok, and gave me the phone number of the allotment secretary of the two sites I was interested in. Mind you, there contact details were a bit out of date, but hey!
When you say that the council weren't informative, do you mean that they said that the plots are all full, or would they not give out phone numbers of site contacts?
You can always look at the list of the sites on the web site and go and have a look round at the site you like the look of most and ask whoever you see who you should contact - nothing like a visit to get the 'feel' of the place!
Good luck with it - let us know how you get on.