Here’s what Building Control have said.
“Thank you for your email.
It concerns me that you now have a leak in your hot water system.
Under Building Regulations we are legally required to complete statutory inspections, unfortunately the work you are referring to is not included as one of these inspections.
As we are not on site every day, we are unable to inspect every aspect of the work, and rely on the builders and tradesmen completing work to a satisfactory standard. I have checked our site records, and although we completed numerous inspections on site, we have no record of viewing the internal water pipes, which is not uncommon.
I suggest you contact your builder with regards to your concerns, and repairing the leak.
Obviously, if you have any further queries, please do not hesitate to contact me.”