if you sign the form with 1% before hand then you are screwed anyway and why even consider about buying through another agent if you saw property through first agent? Tell the agent before signing you will only pay 0.5%, thats the usual practice, if he doesnt agree then move on and find another smaller agent.
Also do not confuse property price negotiation with agent fee, paying full 1% guarantees nothing, agent would still side with vendor because higher the price-higher the fee.. On the flip side, if you start with 0.5% and negotiation is stuck, you could increase your commission to incentivise agent to tilt on your side.. End of the day price of the property is what you are willing to pay so dont let agents run over you, they are double desperate than you to make that transaction through..
Extra rant..
Most of them are scumbags, hardly do anything except bit of legwork and create FOMO, zero post-sale service and the list goes on..