All doors will lock with the fob and its only the drivers side door won't unlock. It still unlocks with the key though. Does anyone have any idea on how to fix this? 

Replace the door latch module.

Cheers, Do you have any clue what the part number is, also would you recommend trying to sort it myself or looking for a mechanic to do it?

39 minutes ago, elliott_norman said:

Do you have any clue what the part number is,

There are a possible 13 different door latch numbers for a 2007 Fiesta. Ruling out the ones for LHD models and other things it still leaves a possible 5. The only way to be certain is to remove your door latch and check the number.

You need the exact type as they are not interchangeable.

54 minutes ago, elliott_norman said:

Cheers, Do you have any clue what the part number is, also would you recommend trying to sort it myself or looking for a mechanic to do it?

Difficult to say without knowing your skill level.  It's not a 5 minute job but doable with fairly basic tools.

As above, need to know exact year, spec, deadlocks, etc to find the part number.

Tom is almost certainly correct in his suggestion, but as the Driver's unlock is on a different output from the GEM as opposed to the other three doors, it might just be worth checking GEM connectors, and A post connector before you start the hours of endless fun accessing the doorlock itself.  I have changed door lock motors on a Fiesta and a Fusion, and as Tom states, "It's not a 5 minute job but doable with fairly basic tools".

With the GEM connector disconnected, it may be possible to put 12V into the door and see if it then unlocks.

You may be able to get the correct FINIS code from Catcar by inputting your VIN, or by tallking to your FORD Dealer.  When you faint at the price of a new one, he might tell your the FINIS code and then you may be able to get the correct one from a well known auction site.