Hi Robin, something else to consider is to buy a relatively cheap one online. I picked up this guy from amazon (
https://www.youtube.com/watch?v=7JMitUg8_Tk) some time back and it works perfectly fine for my needs. After weighing up the pros and cons of make vs buy I decided that it would cost more in additional tools to make one than to buy a cheap one.
Don't expect top class engineering! However, if all you want to do is bend light sheet metal for, say, making enclusures, etc. It does the job nicely.