I agree it will be better buying springs from a company like Spax or Eibach etc, and if you can stretch to affording some then deffo go for it, but if you've got to save up for the springs i'd definately encourage getting the grinder out on your current ones til you can afford the uprated ones.
The only times I cut springs is when I am lowering a car you cant get springs for. But its definately not unsafe, i'll put money on that.