How do i change 12v power / cigarette lighter! in a Peugoet 206

I think its F5 on fuse box of 30 Amp.

do you mean the 12v aux input socket as most vehicle's of that age no longer have a cigarette lighyter, open the fuse box lower dash drivers side list will be on the cover or look in the drivers handbook

Have a look in the Peugeot 206 Manual for the Fuse Panel. This will give you the Fuse layout and where to find it in the car.

Check integrated fuse

When a Bulb starts to flash fast, it is normally indicative of a Burned out Bulb..

check that you have the right type of oil in the car and that you have enough of it in

they have thare own fuse

Replace spark plugs, air and fuel filter. That is ordinary mainteinance.
Ensure that you have spark on 4 cylinders.
Go to a garage and have car ECU (computer) scanned to retrieve error codes. That will tell you where problem can be.
Have vacuum system and fuel pump tested. This is done using a gauge tool.
Have compression tested.
Check O2 sensor, if the problem is particularly bad when engine is cold , also check AIT and MAF sensor.

Check to see if you have power to the fixture, make sure you have a good ground (fixture to dash tight), if all these check out you may have a bad fixture that needs to be replaced.

There is an item called a "setting saver" or something like that. It's a small power supply that plugs into the cigarette lighter, that keeps radio and computer active while changing battery. (I imagine you could make one by attaching a cigarette lighter power adapter to a good battery and plugging it in there.Don't use one with a transformer, just straight 12v!