Does anyone know on which part of the plane the animal goes in?
Pets travel in a dedicated, climate- and pressure-controlled section of the cargo hold.
Just want to know how safe it would be to fly him over if I did decide to bring him over, and has anyone else had a very scared cat come to England before? Where in the plane do they put them? How loud and dangerous is it?
Your vet is most qualified to tell you if he's healthy enough to fly. If he is, then the risk is minimal. If not, then you should consider waiting till he can be booked on the Queen Mary 2. You can also fly Air France, which lets you bring a small pet as an under-seat carry-on, into Paris first, then proceed by land for the rest of your journey (although given his anxiety issues, that might actually make things worse).
I moved with two cats, let's call them Good Cat and Bad Cat. Bad Cat is a prick who thinks everything that happens is in service of her. She believes nothing bad can happen to her (and she has much evidence to back this philosophy). Bad Cat loves rides in the car and took everything in stride; she's about 6 months younger than your cat and, when she arrived home from LHR, she strutted into the flat like nothing had happened. So, although she doesn't have anxiety issues, she is slightly older, and still that didn't stop her being happy as Larry.
Good Cat was only 2, and is the sweetest, most earnest, most anxious cat I've ever owned. She cried all the way to the airport, until she couldn't cry anymore at the IA Cargo office. Broke my otherwise non-existent heart. But I remembered what my vet had told me: Once they're in the hold, and it's dark and basically quiet (the engine noise is a constant hum, like it is for you in the cabin), without stimuli, they just curl up and go to sleep. Particularly cats, because napping is pretty much their best talent.
Good Cat apparently did a lot of crying all the way home from LHR (we opted to pay for JCS's delivery service -- which I highly, HIGHLY recommend, as they're much better equipped to transport your pet into London than you would be with a cab after a 4-to-6-hour wait after a red-eye). But she was fine health-wise. She did a bit of hiding under the wardrobe, because that's her reaction to a new situation (unlike Bad Cat, who took over the couch, bed and cat condo within a half-hour), and it took her about three days to get more comfortable.
Just don't act as if anything's wrong or different. Maintain as much normalcy as possible, and normalcy will be restored quickly in kittenland. When I moved them over, I brought their toys and favourite blankets from home, and that seemed to help the transition. Oh, and my husband had treats at the ready, which of course Bad Cat ate all of because she is a fat (beautiful, fluffy) jerk. Worst-case, just buy his love with treats. Whatever you do, minimise your stress (it's impossible to eliminate), and all will go fine.