Last year I had the same urge to build a simple hydrostatic rig. However I found a complete unit from Vevor for silly money. I think it was £14 delivered. Turned out to be an excellent piece of kit. The only mod I made, was to fit a decent quality non return valve, although the existing one worked without leakage.
There was no way I could even buy the necessary materials for £14. The time saved was put to good use building a spark erosion machine.
Andrew.