If you are flying at a peak time for a flight back to the UK (e.g. between 5pm and 8pm) then I wouldn't recommend the Club MCO lounge. The trouble is that there is only (to my knowledge) that one lounge for that wing of the airport and so it is shared between basically every European based airline's passengers. This means it gets absolutely jam packed with both people who have business class tickets and people who have paid to use the lounge, because it's the only choice.
We flew BA last year and had an upgrade to Club World on the way home, so were entitled to use the lounge for free. When we got there, there was about a 30 person queue to get in (all the way from the lifts to the desk) and they were dealing with it on a one in, one out basis. I peered round the door and it looked like even when you did get in, your chance of finding seats together (assuming you weren't a solo traveller) were going to be very tough and that it was going to be quite noisy. We turned around at that point and just went back to the main terminal and sat down in the seats at an unused gate and ate what we'd bought from the food court and probably had a more peaceful time of it!
However outside of rush hour, it's probably quite a nice place. Also if you were flying with an American based airline (Delta, United, etc.), then because they're in different wings they have their own lounges and these are far quieter and a lot more relaxing.