Whether its worth the extra money or not depends on how far away you are from it.
it seems that Infinity 2 rapidly loses performance over certain distances.
Just because it is FTTC doesn't necessary mean mega fast speeds,the distance the old copper(or aluminium) cable runs from your house to the street cabinet can have a large impact on what speeds you can get.
My house is less than 200m
walking distance from the fibre street cabinet,yet the estimation for the length the old copper cable runs is 861m,which gives me a rough speed of 22mb down and 8mb up(on a 24/10 package with Origin BB)
The chart below was supplied by Thinkbroad,it is for Digital Region,whether its the same for other fibre connections I'm not sure but it will give you a rough idea.