Ask HN: Ethical Hackers / Security Testing

Hi Folks,

my company's about to trial some new public display equipment. We'd like to find a company who can test the security of our solution to ensure that no one can change the messages put out, or disrupt communications with the service. Can anyone recommend any UK based white hat security firms?

Thanks in advance,

JB

ps. I haven't yet heard what technology is being used by this equipment, but am pretty sure the equipment itself will be running apache on linux. I hope to find out more info soon.