We usually fly Virgin into Orlando International, but we've never flown from Manchester. Plenty of people here have, though, so I'm sure you'll get some advice. If you have the Brit's Guide, read up on the chapter about the airport and familiarise yourself with the place - it has a double baggage collection system which is not complicated, but a little unusual. I could give you all kinds of tips for getting through the airport quickly, but I don't want to bamboozle you with too much information on a first trip. The best piece of advice (which you've already received from several people on your other thread), is to remember that you are on holiday, chill out and enjoy it. It is like no other holiday destination: tiring, total sensory overload, potentially stressful (if you don't follow the 'chill-out' advice), but SO MUCH FUN!
To me, Wet 'n' Wild is a concrete eyesore on the side of a road, but then I can't swim and don't enjoy water parks. Given that I have to visit them for the sake of others in my party, I would much rather be at a themed Disney one. I would say that BB has a slight edge over Typhoon Lagoon due to the over-the-top theming.
Yes, I think AK is a must do, but I think all the WDW and USF parks are must do's. I can't imagine visiting Orlando and not doing one of them, but I know plenty of people do. I'm not really up on all the current ticket options as we tend to buy Annual Passes for Disney and Universal. However, I'm sure it would be helpful for those who are able to help, to know which parks you plan to visit (Disney, Universal, Sea World, Busch Gardens, etc) and the duration of your stay.