Hi,
Just did a 100 hour building package with OBA before Christmas. Had done the PPL there also and don't really have anything bad to say about them. Did my hours in the Warrior which are old and reliable. Managed to get the 100 hours done in around 25 days, lost only two days due to weather. If you're prepared to keep your head down and do 5-6 hours a day when the weather is good then you should be fine. Hours in the aircraft are given out by means of a bidding system, if an instructor wants an aircraft they will of course get preference. The dispatchers will however try to get you all the hours they can. Things tend to be a lot quieter at weekends so that's when you'll get most of your flying done. All in all I haven't really got anything bad to say about OBA. Having been there for the PPL and going back a year later for hour building I can say that they have really turned themselves around, a lot less crap to deal with than before. My advice is go for it, fly all the hours you can get and enjoy the view.