My leased GTD is on the longlife interval, which is a dynamic interval.
I rang up the lease company a few weeks ago and said that the count down had come up and was it ok to service it now because I had a convenient window in my work diary. I called them because the VW dealer said "ask because lease companies are funny"
Their answer was that it should be done every 18k and to ignore the computer and that the VW dealer was talking rubbish...
So basically, ask the lease company, do whatever they say!