I am only guessing, as I never took mine apart, but from the drawings, the topside leadscrew is held in place by a bearing retainer (item 10)
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. Remove the handle off the leadscrew (grub screw and nut on the end – Check LH or RH thread ??). Remove the dial after slackening the 2 grub screws. The bearing retainer must now be taken off and I can only assume it is held on by a couple of socket cap screws. – As I said, I am guessing. With the bearing retainer slack, put the handle back on and wind the lead screw and bearing retainer out. The brass lead screw nut is held in place by a grub screw in the end of the lower half of the topside, slacken and drop the nut down. Now the top slide should come off.
OK, so the top slide is being held on by 2 pins with chamfered ends. These chamfers 'grip' the cone on the cross slide. Once you have removed the grub screws they will slide out as you pull the top slide upwards. Now, your problem is that they are not sliding out. I suggest you slacken the gib screws on the top slide and remove the top half along with its lead screw. Apply some gentle heat and WD40 to the rest of the top slide assembly, wiggle it round and round whilst pulling it upwards and it should come off. There isn't any other way as there is no access from under the saddle / cross slide.
BobH