As Mr Wilson says disable it or make it a manual. I recently fitted an electric gate for the first time (I'm an Electrician btw its not my normal field of expertise) and the amount of STANDARDS you have to meet if its automatic operation is ridiculous. As you say children have been crushed to death, hence all the recent stupid EXTRA legislation and EXTRA safety systems you have to install, calibrate and test.
175 notes is a lot but the 'Engineer' now has liability for your gate, Any accidents or damage to people/vehicles and he will have to prove he left it in a fit state after servicing. He sounds confident if he only spent 45 mins there. I breakdown his costs as this.
Labour 75 inc VAT
Liability of installation 100
Health and safety overrides common sense unfortunately and its pricey to boot.