THEORY is nice, PRACTICE is often different.
The thorugh bolts onto the side supports seize, nearly always, and sometimes you have to be forceful and yank them off, breaking as little as posible in the process.
There is a easy cheap, less than £1 cure that will fix the problem PERMANENTLY though so don't despair, if you need to be a bit brutal.
Free off the height adjusters whilst the bumper is off as a lot easier to do then!
tabetha