A bit of googling suggests that
(a) failures of the electric power steering racks of Peugeot 207s are not uncommon; but
(b) power steering problems are often associated with ABS faults (especially if the speedo starts playing up at the same time), rather than with the power steering system itself; and
(c) error messages for the power steering and/or ABS can sometimes be generated through a faulty alternator providing insufficient power to the systems.
All of which would seem to suggest that you need to find a really good mechanic (who actually knows what they're doing) to run some tests on your car before making any expensive assumptions.