Rating of electric cable used to supply cooker panels?

[ppppenguin]

Under 17th ed all circuits (with a few special exceptions) must be protected by RCDs. There must be at least 2 RCDs so that a single earth leakage fault doesn't trip all circuits. The best method is separate RCBOs (combined RCD/MCB) for each circuit but this is more expensive.

It is not permitted to change the fuseboard without testing the entire installation. This may involve a certain amount of judgement as to what parts, if any, need to be upgraded or replaced. Typical issues on older systems may include older 2.5mm cable which has only 1mm earth rather than 1.5mm and lighting circuits with no earth conductor at all. Neither of these is an automatic fail. The smaller earth conductor will be more than adequately protected by the new RCDs and unearthed lighting circuits can be re-used provided none of the fittings requires an earth. All these deviations must be recorded on the certificate that must be issued by the installer.

Also, a consumer unit replacement may only be legally done by somebody with "Part P" self certification approval or by notifying building control.

What happens in practice may be different and I couldn't possibly comment further.