I've been to Tampa via Charlotte on US Airways. Going out was fine - we had to go through immigration and collect our bags at Charlotte but once you've gone through customs there's a clear area for flight connections - you hand your bags back and follow the signs.
I would recommend scheduling a couple of hours between your connections to account for any delays and because immigration can take a while. But there are some bars and restaurants in the terminal to keep you busy.
Also if you buy duty free booze in the UK you'll have to put it in your suitcase once you've collected your bags at Charlotte - they don't allow the liquids on board even though duty free will put them in a sealed bag.
The terminal is not too bad - I think it took about 10 mins to walk to our gate.
I can't remember how long the flight to Charlotte was but the flight down to Tampa was about an hour - hour and a half I think, so I guess Orlando would be the same. It was fine, the only difficulty is that a lot of the domestic passengers have huge carry on bags which take up lots of room in the overhead lockers so if you can minimise your hand luggage it'll take out a lot of stress! As you've already been through immigration once you get to MCO you can go straight out
This year we're flying with BA as it was only slightly more than US Airways for our dates, but I would happily fly indirect again if the price was good
