I primarily use cut-off wheels on air die-grinders. Here in the US, the wheels come in various diameters from 3-5" either 1/16" or 1/32" thick. In tight spots I use a Dremel tool mostly with the reinforced cut-off disks. I've occasionally used electric angle grinders with cut--off disks, but the air tools are a lot smaller and lighter and generally a lot easier to use.
I find that many of the areas I'm repairing don't have enough room behind them to use saw blades, but when I can, I also use an air-reciprocating saw. Mine is an I.R. Wish I could find good blades for it - they don't last long.
I have a plasma cutter, but haven't really found any use for it. I've only used the acetylene cutting torch to cut up bodies I've junked. Neither make very precise cuts, although maybe the plasma cutter requires some learning. I have a Henrob gas torch, but haven't used it yet. It looks like it should make a much finer cut than the traditional cutting torch.
I use 'aircraft' snips a lot too: old ones to cut up rusty metal, newer ones to make patches, etc.