[chuzz]

Well, it sounds to me like you've just got a loose starter cable. Disconnect the ground cable and check for good clean connections on both ends first. Then, remove the positive cable and check the connection on the starter. Make sure these are also clean and tight. And clean the posts on the battery and your connections before attempting a restart. I don't know anything about the CRD engines since they're not available in the U.S., but this is just a basic electrical connector problem, I think.

 

[ImperialCrown]

You may want to access a service manual with wiring diagrams. The main and fog lamps coming on along with the 'no crank' seem to indicate to me a wiring harness and/or underhood power distribution center (PDC) problem. Wires may have shorted or melted together. Moving some components out of the way to investigate this possibility may be necessary.
Multifunction switches here had problems with the fog lamps staying on and discharging the battery, but if yours only come on with the ignition switch on, it may be a different problem and probably points back at the PDC or wiring harness.
Does a malfunctioning immobiliser prevent cranking? We don't have that type of security system in the states either.

 

[jimbobUK]

ill try my best to trace them back. i found the way to get error codes and it came up with 2 p0703 and p1685 but on the brakedown guys computer didn't show anything.

P1685....Smart Key Immobilizer Module has received an invalid key.. strange i have 2 sets of keys both dont work

P0703 Brake Switch Circuit Malfunction .. brakes working fine but this was changed way back looking at the service history also this would not stop the car starting ?

 

[ImperialCrown]

The brake pedal switch (not the rear lamp section of the switch, but the PCM ground sense section of the switch) may have an issue, but this isn't the no-crank problem.
The P1685 is probably a good clue to the problem. If both SKIM keys were working fine before, then both stopped working at the same time, then I think that the problem may be the SKIM module, wiring harness or PCM and not the keys themselves.
Which 'possible cause' it is, may require a diagnostic scan tool that can look deeper into the modules. Like 'starts since set' and the freeze-frame information that took a snapshot of the various modules at the setting of the fault might help complete the picture.
For now, see if you can rule out a wiring problem.