Hello, i've been watching lots of videos about the timing belt of the 1.25 fiesta, and in some of the videos the people loosen the cam sprockets and put the new belt on and some others seem not to loosen them and just put the new belt on. In the cases where they've loosened the sprockets it doesnt show them then tightening them once the new belt is in place. I am basically wondering what the correct procedure is? I am also wondering whether it is completely neccessary for the flywheel to be locked? As some people online seem only to lock the cams.

The sprockets should be loosened.  (And definitely tightened after!)

Loosening the sprockets allows the correct belt tension between the two cams without the shafts moving.  It will still work without loosening them, just not 'best practice'.

The flywheel doesn't have to be locked as the crank can be locked using a bolt in the back of the engine block.

16 minutes ago, TomsFocus said:

The sprockets should be loosened.  (And definitely tightened after!)

Loosening the sprockets allows the correct belt tension between the two cams without the shafts moving.  It will still work without loosening them, just not 'best practice'.

The flywheel doesn't have to be locked as the crank can be locked using a bolt in the back of the engine block.

How would you know you have tightened the sprockets to the right position once the new belt is on? Or is this not really an issue?

8 minutes ago, Hawky03 said:

How would you know you have tightened the sprockets to the right position once the new belt is on? Or is this not really an issue?

It doesn't matter.  What matters is the shaft position, not the sprocket position.  So the sprockets are in the right position once the slack is removed from the belt by the tensioner.  That's when you tighten them.

2 hours ago, TomsFocus said:

It doesn't matter.  What matters is the shaft position, not the sprocket position.  So the sprockets are in the right position once the slack is removed from the belt by the tensioner.  That's when you tighten them.

Also, so once the lock pin is in and the plate is locking the cams, can you use the impact wrench to rempve the crankshaft bolt? Just seems that lots of people have their own way to do it all.

22 minutes ago, Hawky03 said:

Also, so once the lock pin is in and the plate is locking the cams, can you use the impact wrench to rempve the crankshaft bolt? Just seems that lots of people have their own way to do it all.

Yes that should be fine. 

There is some chance of bending the crank locking pin while loosening the crank bolt which is why locking the flywheel is a good idea for that part.  The flywheel lock isn't needed for timing though, perhaps I should've clarified that earlier.  As you say, different people choose to do it different ways so it's up to you really.