Re: ICAO codes for Origin and Destination when passing details
I don't think I would use just the ICAO codes. I sometimes use both the names and the ICAO codes especially if I'm fly to or from somewhere a bit out of the way (or anywhere French because I can't pronounce the names!). So for example I'd tell East Mids that I was going to Weston EIWT or St. Brieuc LFRT, but if I were going to Wolverhampton, I'd just say Wolverhampton.