Steering
Front wheel alignment
It is not made clear in any documentation I have seen however our Peugeots should Toe-IN about 8' (8 minutes) - about 0.75mm - on each front wheel. (I set mine to 1.25mm on each wheel as suspension is sure to be weaker after 13 years). Castor and Camber cannot be altered and are fixed provided the top mounts are in good condition and in the correct locating holes - see here - and assuming nothing is bent out of shape.
If the car pulls one way then look for a bent suspension part - a broken spring might have damaged something else (possibly on the way to the garage - they are not always careful where they attach their tow rope)? Also - check the rear suspension tyres and alignment; they can be damaged the same way as the front and will also affect the handling.
Do have the alignment checked at a well-equipped garage - cornering on both our cars is very neutral and the cars drive straight even with hands off the wheel. In brief - get any waywardness checked out on a good alignment machine.
Electric Power Steering
It can occasionally fail - you still have steering but it becomes very heavy.
The power steering is electrical - so if it fails, try a battery reset - to ensure the electronics reset to their initial values.
Should the battery volts drop (due to a faulty battery or alternator) the BSI cuts out some unessentials - air con; radio; power steering to give you the best chance of getting home before the ignition finally packs up.
The steering ECU is at the rear of the battery box - remove the battery for access.
Failure can also be due to an electronic glitch (often resets itself) or rarely by a poor connection onto the steering rack motor. Be aware that this connector is hard to get at as the connector sits close to the starter and the rack and pinion. The only access is to either lift the vehicle up on a ramps or to take the battery box out.
shows the general layout of the steering rack
shows the individual components of the steering rack
(Info from JoJo) Occasionally power steering failure can be due to the sensor in the rack failing. It is fitted on top of the motor with the loom coming from it on top of the rack. The rack can be taken off a scrap car and fitting the whole assembly isn't too difficult.
Apparently this sensor fails on other PSA group cars including a few Citroen C3's.
Symptoms are that either the electric steering fails completely or at standstill the wheel will twirl full lock right or left or exhibit general erratic behaviour.
I hadn't used the yellow car for a week but had been doing little odd jobs on it leaving the doors open; radio on; polish headlights etc.
Jobs done and drove off - NO power steering. Down the road - still no power steering. Parked up for an hour; started engine and power steering now perfect (and again for the return home).
Happened to the silver car in 2011 - no power steering after an MOT. Drove it around the block and perfect ever since.
Just be aware that something (possibly the BSI) can kill the power steering, but that it returns of its own accord after one or two starts.
Apart from the sensor failure above, I have yet to hear of any failure of the actual power steering motor or mechanism. Update April 2018: there has been one report of "cracked rack" at an MOT test