You can get sensors for around £20 each , genuine ford are £170 each , I used them and they've been fine so far. Mine had the same fault just replace them , if the cars running rich then it's either lambda sensors not reading right or you cat if fucked. If the code is the sensors then it's them that's why they have ob2 diagnostics to pin point the fault
Make sure you buy the sensors with the Ford connector and not a universal one as you will have to cut and crimp the cables.


Cheers Paul