Had a cracking session yesterday!  The UJ has been drilled to allow it to be attached to the base, and I've made the plate that the main frame will attach to.  It's made from two 200mm lengths of 50mm wide steel plate welded together and ground down.  Now I just need to weld the supports to it! (Potentially easier said than done...).  Also, I've decided that I'm not going to be able to get the hydraulics in and sorted by the finish date, so instead I'm going to use a couple of electric actuators to show what movement would be available.  It's not an ideal solution, but at least it will move!