I'm intrigued that it won't do a purge cycle. Turn it on and (before the engine management and glowplug light have a chance to go out) press the accelerator five times in quick succession. You'll hear the pump going on and then off again for a few minutes, whilst the engine light flashes. If everything else works, that implies that the ECU is doing something weird. Have you got access to a diagnostic device you could try? I'm sure you know this already, but the TD5 isn't fully OBD compliant, so the average generic fault code reader may not be much help. A lot of us on here favour the Nanocom, but the Britpart Lynx is also available and has the advantage that you run it on a laptop so you actually get a decent screen and keyboard.
