Right the builder has been back today, he said that the electrician has had to self isolate and conduct a COVID test. He said the electrician will come back after approx 5 days if the test says clear. The electrician will come for testing and updating the installation report.
The electrician advised him to update the oven wiring. So now behind the oven, the oven cable goes to a mounted white plate which has no switch. I understand this to be a 20A 1 gang outlet plate? Directly next to it is the 1 gang outlet for the gas hob ignition. I understand that these are wired so the cable goes from the switchless plate, to the 1 gang switch, then to the cooker isolator switch. The hob ignition I understand is on a 5A fuse.
The breaker for the circuit has been changed to 16A. I asked surely if the oven happens to draw near to its max and you boil a kettle at the same time (or run dishwasher), it will be too much current and it will trip the circuit. He said it's not a problem and phoned the electrician to reassure me that it will "definitely" be fine, and talked about how the RFC is two 2.5mm cables so it is like having 5mm. They were speaking in their local dialect together, so could not hear the whole conversation.
Can you confirm to me what has gone on here is not a viable solution, and is a bodge job to get the oven on? If the kitchen circuit was intended to have a 32A capacity, it must be impossible for it to be magically sufficient to have a 16A capacity for dishwasher, kettle, toaster and portable appliances on the same circuit. We ran kettle, fridge, microwave, oven (on fan mode) to see if it tripped, but it worked OK. So that was his demo of "all ok".
I probably should have said don't do anything at all after I heard the plan, which was delivered to me on the spot when he showed up. But I had their assurances and that they can come back if there is any issues, so I agreed with trying their suggestion incase it is my own misunderstanding of how things work.