Catkin, a couple of observations. First, the grid has 180 degree symmetry. So every time you put in one bar, you can enter another as its reflection. Second, there are no two letter words in the grid. So if you see two cells together, as in the four top left cells, you can put bars between them.
After that you will need to start by using the left hand and right hand pairs of columns, as you know which answers fill them, and try to make words. Work on the assumption that the left and right columns are 6,6 until proven impossible.
After that, you might try and see if you can make eight letter words across. It’s not easy, and there are many obscure words. But I found it a fun challenge