Awwww, thanks Jez!
Whens that Ringle stem coming?
Follow that link to ebay for a flypress to visualise it. It works by rotational movement of the handle on a very coarse thread to give relatively fast downward movement of the mandrel. One of their main uses is for punching holes and shapes in sheet metal. I have a range of punches and dies for a flypress, the male part fits into the mandrel and the female in the hole in the base. Place a sheet of steel/aluminium/brass etc between the 2 and rotate the handle - the punch comes down and punches the shape out. Its very handy for mounting electrical connectors as they are usually an odd shape. The tools are on the expensive side though. I also have a range of tools to bend sheet into fabricated boxes.
You can also use a flypress for straigtening out bent tubes etc as the pressure exerted can be controlled quite easily as you can feel what is going on.
A hydraulic press works like your car jack. You pump a piston which in turn forces a ram down towards a table where your component is sitting. A pressure gauge is attached showing how much force is being applied, I have a 30t one which is an average size for general engineering, but they are available 200t+. You use this type of press for assembling components that require an interference fit where the shaft is bigger than the hole it is being fitted to, eg bearings in a housing, or bushes in your car wishbones. A hydraulic press also has the advantage of being able to exert constant pressure, so it can be used to make sintered components. One disadvantage is that you have less feel of what is going on, unlike a flypress.
Hope that all makes some sort of sense!