does the 2005 model fabia stereo (symphony) use standard ISO connectors?

I would say almost certainly yes

thanks

Yes it does , but there are a couple of changes to the way they are wired up.

The permanent and switched 12v wires are the opposite way round to standard so will need to be swapped over if you fit a replacement HU.

Also one of the pins is used by the car for diagnostics (K line if you are searching for more info) and some (but not all) car stereos output a 12v signal into this pin. That can damage the diagnostics computer at a dealers if this is the case. You can get wiring adaptors to make the necessary changes , or do it yourself.

thanks for that, i was intending to replace the standard stereo myself with a parrot rhythm n' blue, for use with my bluetooth phone.

now thinking just go for a standard car kit wired to the existing stereo.