My small flat required an Electrical Safety Standards Certificate. Cost £120. The electrician said that the consumer unit needed replacing. His charge for doing this, £350. The unit cost £37, any competent electrician could have removed the old unit and fitted the new one in 2hrs max. I had to accept this bec the tenant was due to move in 2 working days later. He also charged £150 to earth the gas and water supply, this was a task that probably took 3hrs.
When I challenged him about the cost he did not charge £120 for the safety certificate.