The Airport Tour centre is really a presentation / classroom and also the admin offices for TAS. to visit I think you would have to be on an organised tour. Theres not a great deal to see just loads of photos and a few bits of memorabilia. The great view it once had has been blocked by the terminal extension. The actual tours, tour the terminal and the tour centre is used for showing films etc.
PB Enterprises(aero) was formed by Peter Hardy and friends, it used to meet in the rear room of the "Airport Hotel" pub (at the end of runway 24right.
They used to run regular aviation coach trips all over the UK, I am not sure why it disbanded.