Ford Fiesta Finesse 2003

Fold down the other seat and look between the flat and see if anything is obstructing it from moving push the leaver and make sure it's hooked up

Fuel pump can be accessed through a cover under the back seat.
Note: Before pulling the fuel pump check the fuel cut off hasn't been tripped, it is inside the drivers or passenger kick panel. Your owners manual will show how to reset it.

normally the seat tracks are bolted to the floor or riser. It is possible that when the seat was moved forward the track moved over the head of a mounting bolt and will not return. check for interference between track and rail while trying to return seat.

dealers repair book best option/mechanics manuals may find online

mechanism lower seat driven by electric motor is broken.

If I remember right, the coupe models would allow you to slide the seat forward if the seat back was folded to allow access to the back seat.
You will probably need to take the seat out of the car and turn it over to look at the linkage. There may be a broken spring or rod that is not releasing when you try to move it.

There should be latch on the lower right side of the seat. If this not working properly the seat wont release from the lock.

Register at www.autozone.com (it's free). Once registered you'll have access to several repair manuals that should show how to fix it and what part you'll need. You can then get the part from a dealer or save $$ and gert it from an auto parts store.

youcannot fix it you have to replace it

IF YOU JUST NEED TO FOLD THE SEAT DOWN LOOK UNDER THE BACK OF THE BACK SUPPORT, YOU SHOULD SEE A CABLE ( BLACK) PULLING THIS WILL RELEASE THE CATCH TO FOLD THE SEAT FORWARDS

there is a cable that is attached to that and goes down to a release in the bottom of the seat, find it and you will be able to release it.