Peugeot 307 2.0 hdi turns over but refuses to start

Without plugging the car into a diagnostic computer to view live data and fault codes you're really stabbing in the dark.

The Peugeot hdi engines will usually start without heat down to freezing temperatures so its unlikely for the glow plugs to be the issue.

When you replaced the fuel filter did you bleed the fuel? There's two ways of bleeding it depending on the fuel lines, if there is a fuel 'bulb' on top of the engine connected to the fuel lines then keep squeezing this until it goes hard. If there is no fuel bulb the car will have a in tank pump, to bleed this system turn the ignition on and you should here the pump run and a rush of fuel flowing through the pipes, when it stops repeat until the rushing noise stops.

When you turn the ignition on does the engine light come on? The engine light should come on with the ignition and then go of whens its running. If the engine light doesn't come on with the ignition then there is a communication issue with the ECU.

A common fault with this car is water ingress in the multi-plugs of the engine ECU, disconnect the battery and pull the connectors to the ECU and check for water or corrosion.

Without using a diagnostic computer you can check if there is fuel pressure by undoing a fuel pipe to a injector and turn the engine over and watch for fuel. Be very careful doing this as there pressure in the fuel rail is several thousand PSI.

Without a diagnostic computer that's about all you can do, I would either get the vehicle to a garage or have a mobile mechanic to come and get the fault codes and look at the live data. In the UK a local garage should come out for anything in between £50-100. You then have enough information to diagnose rather than just swapping parts for the sake of it.