Just screwed - I used a drill/driver, too many to do by hand! I use screwfix turbo screws - more expensive than normal screws, but in the grand scheme its not a big difference in cost. However, you dont need any pilot holes and they dont split wood.
Simple butt joints all round. Top strut screwed with 1 screw into the end of the uprights. At the bottom, I changed the orientation so I had a wider area to screw into and put 2 screws in each side (could have used bigger wood, but I just bought a lot of the same size). I figured that the weldmesh would pretty much keep the frame straight (it did). The weldmesh was stapled on, 10mm staples using a carpet stapler. Stapled on the outside to make it more foxproof (cant push it in). Note that I dont have a waist-height cross beam on the frame., so I needed to put the mesh on the outside.
I wasnt sure the diagonals were really necessary, but it does make the frame much stronger and doesnt take much effort, so worth doing.
DEFINITELY put the weldmesh on before putting the panels up. I put the panels up one at a time on to the sleepers - take time with the first one with a level etc, and then the others are easy. Use a spare bit of wood (or willing helpers!) to hold the panels in place until they are all connected together. The beauty of using screws is that you can easily 'tack' bits of wood together to keep everything in place, then remove them later!!
To actually attach the panels I used 4mm (#8) x 100mm screws. You definitely need a drill/driver for that. Using the turboscrews comes into its own here, they just go right in.
Three screws down the length to hold one panel to the next.
NB- the sleepers were 'fastened' to the ground by driving a few posts either side into the ground, then screwing through the posts into the sleepers. They will probably rot eventually, but now the frame is holding it all together.
I have close-up photos which I'll post tomorrow once I reduce them, too big to put in tonight!