I'm trying to work out which I've seen and what the current situation is. I've referenced here and the wagons forum for sightings etc... and this is the best I can come up with.
Gantry - Last sighted wagon / Date
89110 - 979614 28/10/14 going back to 2011
89111 - The gantry is stored at York, but I've drawn a blank on which wagon it is on. I believe it is the one stored the Holegate works side of the line & hiding in the vegetation.
89112 - 979607 - March 2014 going back to 2011
89113 - 979613 June 2012 - This is also stored at York & I believe they are between the NRM & FL depot, along with 979511 & 979513 from other peoples sightings.
89114 - scrapped 2008
89115 - 979609 - May 2014 - Jan 2012 - However, there is a period around late 2014 / early 2015 where the gantry was sighted at York but the wagon at Eastleigh. It is of course possible that they worked between the two places (there is enough tine between sightings for this to have happened).