Well if your local suppiler will not let you try out a system your interested in, perhaps you could 'hire' it from some else to see if it's up to the job.

I've been out twice this weekend.
First night I wasn't happy with the sound (speakers in the corners, behind the band. Not ideal!) I was beginning to think the rig was showing it's age.
Sounded fine last night.

As you've got keyboards to put though them, I think you are going to need at least 15" bass drivers to handle the lows keyboards's throw out. If it was just vocals, 12" would be fine.

I saw a ad on ebay reciently, "selling all our PA gear, as we are now using a Bose PAS", so it appears that these systems are avaiable in the UK. Still have my doubts about them, but I could be proved wrong.