This seems impossible to find, but I am looking for a lossless version of Vangelis' FYC promo of Alexander, with the two unreleased tracks and the one alternate cue. I may well be wasting my time but does anyone have it, or know where I can get it?

Highly doubt you'd find it, but all I can do is second this request. I have never come across any version of it myself, but I have seen it listed here and there....

Any luck?

Not lossless, but those tracks you are looking for are included in this release:

http://forums.ffshrine.org/f92/vangelis-unofficial-official-bootleg-thread-lossles-non-94478/8.html#post1952611

I hope it helps.