I finally got my hands on one of these and decided to strip it tonight. I am stuck for a barrel pivot lock nut and have asked on of the bbs good guys to help out.
This is a basic pistol and oddly seems to share no parts with the Relum Hurricane underlever pistol


The is a big screw that passes through the pistol grip. If you undo that, the action will lift out of the grip.
With the action out, you can tap the trigger pivot pin out of the housing and remove the trigger. Do the same with the sear pin and slide that out the back of the housing, watching out for a sneaky little coil spring (mine didn't have one but I found something suitable when I put the gun back together) that sits between the underside of the sear and the trigger housing. There is what appears to be a 3mm trigger adjusting screw in a lug, if you want to clean and lube that.
Knock the cylinder end pin out and remove the endcap and mainspring. There didn't seem to be a lot of pressure but I am not sure it is the right mainspring.
Undo the barrel pivot lock nut (if your pistol has one, unlike mine). and remove the breech block from the jaws. You should now be able to push the cocking arm backwards in the cylinder until it will lift free (like a BSA Cadet or Major). The piston can be slid out now.
If you want to clean and lube the barrel catch plunger, knock the little pin holding it out and remove, clean, lube, replace now.
It is interesting to note that your barrel may slide out of the breech block as is seems to be secured by the barrel pivot bolt. If it bothers you, a little thread lock could be used I suppose.
I didn't remove the little grub screw on the underside of the cylinder that hold another plunger as I did not think it was worth doing.

The piston has a leather piston washer held on by an aluminium rivet. It was a bit loose so I spread the rivet a bit.
Clean everything and go to pt2