Mudfoot's about right but there are a few versions of what Airbus call the Elite - a sort of corporate version - going to a few other operators. It's more than just 1 at Comlux, I think, and NAS in Saudi have some sort of commitment as well. Airbus was showing 90 sales for the A318 last month which ain't that hot, all the same.
It will be interesting to see if the London City thing will change the A318's fortunes... if you look at who is flying into LCY today with Avro RJs (Lufthansa, Air France, BA, swiss) plus some of the other guys going in there (SAS, Air One) they're all A319, A320 or A321 customers. I would have though that Airbus has a good shot at this lot. Embraer have mentioned the E190 to go into LCY but it has some performance shortfalls (my quick sums show not better than about 300 nautical miles out of there on the worst runway and given a small credit for headwind). That's not really enough - the E190 and E195 both have a major problem in field performance. A bit odd, I think, for a regional aircraft to have problems at regional airports. Good for the U.S. market, though. Oh, unless you want to go to Phoenix or Las Vegas, that is!