Proper leather shoes

Patent is a bit OTT for most things>>>>
I rock a nice plain polished black leather oxford for formal occasions.

I almost agree. With box calf leather one can get a much better shine than with patent--- its just a lot more work (ask any soldier). That said patent leather has had a kind of come-back making it also suitable for edgy casual wear.

Having said that, I went to an industry (engineering) "awards dinner" recently and there were twunts there with all kinds of their own "interpretations" of black tie,

The problem I think is less the people that show up wearing cowboy boots and jeans to "white tie" events than those that print "black tie" or "white tie" on their invitations meaning instead to say "shirt and shoes" to the former and "clean shirt and shoes" to the later :-)

To be honest, of course, there is no single formal day, "black" or "white" tie evening costume but a number of local rules and protocols and they are not wholly fixed in the 19th century. These days, for instance, tailcoats are no longer de rigueur to an audience. Women at Ascot can wear any hat they want but not even the Queen of England is allowed to wear white when meeting the Pope--- white is reserved for Catholic Queens.

Guides associated with the name Debrett in the UK, Knigge in Middle Europe and Emily Post in the US are quite common.