These engines do suffer from cracked heads. Fitted a brand new head (non-genuine, italian made I think, can't remember the make at the moment, but Turner engineering sell them)to a friends 10P TD5 as it had cracks in four combustion chambers, from the glowplug holes IIRC. They can also suffer from cracks around the injector seats at the top causing diesel contamination of the engine oil.
Oil migration from the injector plug through to the ECU is common and causes misfires. Don't think I've code read one of these without injector codes yet.
The Nanocom diagnostic tool works quite well on Discoveries and Defenders (not perfect, but what aftermarket tool is?) and only a couple of hundred quid.
Hope this is some use.
Shaun