Queueing. You're right, this is the correct spelling.

Queuing I have certainly never heard of, can you really use it? I would have corrected it if someone gave it in to me!

Sorry, if someone HAD GIVEN it in to me. (My mind was on my dinner, I'm hungry)...

verb (queued, queuing) intrans 1 (also queue up) a to form a queue; http://www.chambersharrap.co.uk/chambers/feat...

v.
verb (queu•ing or queue•ing)
1 [v] (BrE) ~ (up) (for sth) to wait in a line of people, vehicles, etc. in order to do sth, get sth or go somewhere: We had to queue up for an hour for the tickets. Queue here for taxis.
http://www.oup.com/oald-bin/web_getald7index1a.pl