(This is dated June 2012, but I got the press around December 2011 sometime)
Here's some pics of my hydraulic press. It's a pretty standard design, and there's lots of these going around on EBay, Machine Mart, Screwfix etc. This is a 20 ton model and I think it was around £100 at the time.
It's based on a bottle jack. The guide and ram leave a lot to be desired - there is around 1cm of sideways slop in the ram, so you have to be careful where you apply pressure to parts. I made a little handle for the vent knob so it's easier to release.
For greatly increased accuracy, it's possible to buy die sets (e.g. http://www.wdsltd.co.uk/products/Standard-Parts/Die-Sets/) which consist of two ground plates with guide pillars, to which can be mounted any sort of press tooling you like. The guide pillars ensure precise alignment of the upper and lower parts of the die.