Plumb London

Sent a plumber called Pavel for a call out fee of 75 pus VAT, plus £30 for every extra half hour. took credit card details in advance.
Pavel quoted 2 hours plus parts for changing a valve on a cistern — Around £300. When I questioned it — he offered to walk away and just have me pay the call out charge of £100.
It was clearly a straightforward job. But he appeared to drag it out as long as he could and at least over the hour mark. Still could only drag it to 1 hour 15 minutes. Then tried to charge me 2 hours. Luckily the office confirmed I should only pay for an hour and a half. Pavel started complaining loudly and told me to my face that he should have dragged out the work longer.
The main office seem to be honest and straightforward — but they clearly need to improve the screening of the plumbers they use.
Pavel seems to be competent as a plumber but unprofessional in engaging with customers. When he initially came to the house only my wife was there. I was so worried about the tone of his language and his overall conduct I rushed home to deal with him directly.