Yep, peterpoddy's the man with the pdfs, however…
To remove the 'spring' action you need to take the damping cartridge out. This would require a tiny allen key for the floodgate knob (these are super easy to round so make it a new allen key as well!) and some circlip pliers for the poploc knob.
A 26mm socket unscrews the top cap and the whole cartridge will slide out. If you do it slowly enough you shouldn't lose much or any oil as you do it. Alternatively buy some knew fluid and just replace the lot, at least that way you can be sure you've got the right volume.
Once you've taken the cartridge out you'll see a little spring wrapped around the inside shaft. Its awkward to get to so you'll need thin needlenose pliers or a bit of ingenuity with a screwdriver. Once unhooked it will stay in place so you needen't worry about removing it entirely.
Then screw everything back together, and buy the replacement knob kit for £10 or so, or bodge the poploc top cap and use that.