We too are from the UK, and are sailing on Liberty of the Seas in October (Western Caribbean itinery). We have also booked a 10 night med cruise for August 2008 and the cost is so much higher. We have an OS on Liberty and only a JS
on Independence and it has cost us an extra £1000!
We wanted to try a Med cruise for a change but I definately feel that the Caribbean is better value. However when you have added flights etc. I guess there is not much difference.
What is your itinery?
We chose the 10 night one for cost purposes, we visit Gibraltar, Barcelona, Vigo and somewhere else I can't remember off the top of my head! I think the Med cruise will be more about enjoying the ship as we have more time on board that on our 7 night Caribbean cruise. We are looking forward to comparing them!