Occasional smell of diesel from the engine bay
 

Every so often I get a smell of diesel from the engine bay , I've checked the usual points ,O rings to the fuel filter and the fuel lines , the pipework to the injectors , the leak off pipes , the top of the engine is bone dry , I'm now thinking it might be the high pressure fuel pump ?

The HPFP is more than likely the culprit. With the engine running you should be able to see any leakage of diesel.

look at the front offside underneath - if it's wet with oily substance theb it's the HP fuel pump leaking (most likely).