The trailer is not a major problem to rebuild. But there are a couple of points to note:

• The gas strut in mine was not comparable to anything on the standard fleet of cars out here, but the local fitment centre were happy to take it away and have one made to match. Did not even cost much - but it did take a week or two. The unit as fitted is a modified truck cab damper by the look of it - similar to the struts on a car boot, but shorter and thicker. They did not give me the specifications but I think it is around 700N (157 lb) preload.
• When the time comes to extract the whole lot, make sure you have removed the grease nipples, they protrude and foul the inner workings.
• Make sure the stroke length of your gas strut is right - if it is too short you have to overcome the gas preload to set the reverse lock. This can be impossible, let's not go into how I found out.
• In case you, like me, have difficulty working it out: you dismantle the hand brake assembly first, remove the grease nipples, remove the bolts fitted radially around the front collar, and remove the bolt that is cunningly hidden in the tongue, just in front of the body of the trailer. Then it all slides out, without much force required, mine did need a little persuasion to break the corrosion around the front collar.

With a clean up, and new grease and damper the trailer is a pleasure to tow.