So..... I swapped the trees over also made and installed a mini irrigation system.
I removed all the decor then heavily misted the ground until most of the colony returned to the tree/nest. Once I was sure the majority of workers had returned, I lifted the tree straight out of the viv making sure not to bury any stray workers. I then went round with the mister and some cotton wool picking up any stragglers. I placed the new tree in the old ones spot and backfilled it with LECA , spagnum peat and vermiculite to try and raise the amount of water the island can hold. I placed the irigation system on top of the base of the tree and covered it over with rocks and bioactive substrate.
I made the irrigation system by getting some small tubing and melting holes in it every 10mm with a pin. The reservoir was made by using the top (clear part) of a birdfeeder similar to the picture below, I turned it upside down and drilled a hole in the side for the tube to connect to. I siliconed some mesh over the top to prevent workers from getting in there and drowning when I fill it up. I didn't take pictures of it during construction but I will include a picture of it in place.
Now for the problem... I saw a small group of workers swarming over some leaves but they didn't end up weaving a nest which i thought was odd. Today I came home from work to find loads of brood in one test tube and the queen and more brood in the other. I'm hoping this is just a transition from the old nest but I'm slightly concerned as they didn't do this when I received them.