I did look into it - but LRSeries shows conflicting info for which switches fit which - with some listed as fitting both 2.5 petrols and diesels, and some just for the diesels, eg:
http://www.lrseries.com/shop/product/listing/1608/579085-IGNITION-SWITCH-ASSY.html?search=ignition%20switch&page=1
From what I can tell the diesel switches should have two spring loaded positions - ignition on, then sprung loaded for glowplugs, then a second for cranking. Mine's got one as per a 'normal' car for cranking only...
Mine seems to be a bit of a bitsa 90, with it's non military 2.5NAD VIN, Ford petrol engine and all sorts of other bits changed around, so I'm never sure what's original and what's not! The 2 diodes only cost me a quid and look to have sorted it, so I can't really complain!