Hi there We've got a gas fire with that sort of fake coal stuff that you're not really supposed to move about, and a large marbly hearth, so I think DS is going to have to be kept away from it, but OH is not keen on screwing things into the walls (that were redecorated not long ago)
Are there any fireguards that don't screw into walls? And are they still safe or can the child climb up onto them and pull them over onto themselves?
Any fire-guard complying to British standards will have instructions to fix it to the wall. Weather you do this or not is your choice. HOWEVER should you not, you have only yourself to blame should your child manage to move the fire guard and get hurt.
Having a fire-guard around the hearth DOES help prevent heads banging onto stone.
2 little screw eyes in the wall is not a major eyesore. When our stove is on AND DS or other children are about we have the guard in place clipped to 2 rings in the wall. Rest of the time the guard is folded up in a corner and the rings are not noticeable.