Thanks for the very fast feedback. Replies are as I expected - I'm just clutching at straws. Someone had (obviously incorrectly) told me that as I had the Qatar RP a letter from a Saudi company was enough for visa on arrival). I have tried to contact the Saudi Embassy to get somewhere but it takes endless phone calls to then just get referred to someone else and no actual answers. Finally got the direct number for the Head of Consular Affairs but always no answer or busy line.

An agent has my passport and had put through an application last week which was rejected because my support letter was from the British Embassy in Riyadh which is not good enough here (same letter worked for all of my colleagues at the Saudi Embassy in London). Agent (El Medadi) says nothing is possible until after the weekend and I might get a decision on Monday or Tuesday. Problem is I have flights and hotels starting tomorrow afternoon and a full meetings itinerary.

Seems there is nothing to do but miss this trip and start over.