And a detail shot of the lever.  Note the small locating whole on the top platen.  This is a slight amendment to the original design and it should work fine.  The depth of the polystyrene in between the platens here is 250mm, but we can fit deeper plates underneath as required.

This is the fully constructed press.  The components are all put together, the wood is yet to be finished and stained.  The lever mechanism appears to have worked very well, and Maurice pulled it with his whole weight and there was not a creak or sign of movement from the press, which is brilliant. 
The next stage is to test the pressure of the press and make any final tweeks to the lever mechanism if needed.  I am confident it will print relief plates wonderfully, but I secretly hold hope that the pressure will be high enough to print intaglio.  We shall see!