Judging by the Forum comments above, I am on a completely different wavelength to everyone else. I thoroughly enjoyed the puzzle. The Wikipedia entry on the system's deviser gave me all I needed to fill the grid, and it introduced me a new area - so thanks Artix.
My problem is that I am struggling to parse too many clues so cannot get to the instruction. Can anyone help me with 15 across, 25 across, 1 down and 3 down. I simply can't work out the surplus word in these cases.
Thanks to all - lovely day on the east coast. There are some advantages in living half-way to Lithuania..