if there is a court date set that would help a lot...as Vicky mentioned a letter from the solicitor could work as well...I am the US half of this relationship and was the one getting the divorce, however I should think which side it's on shouldn't matter so long as there's proof the divorce will be final and you will be free to be married within the 6 months.
Mine wasn't in the end thanks to shady dealings by my ex but you REALLY dont want to find yourself in that position!
The second time around I got a letter from the judge himself to tell them there was a court date..if thats possible it ccertainly wouldn't hurt.
Good luck