You have already fast forwarded a decade or more by stating “the 18th edition of the Wiring Regs� when the 17th has, on the grand scale of things, only been about for a blink of an eye…albeit the amendments to the 17th have just happened fairly recently.
And the fact that this kitchen (special location) seems to be within England or Wales, then its not just the Regs but ensuring compliance and certification in regards Part P of the building Regs…unlike Scotland-shire where its building warrants I believe.
The poster could do the work themselves, but by not being able to self certify they would need to pay an eye watering fee to the LABC to inspect / sign the work off.
Be easier to simply get someone that can self certify
http://www.competentperson.co.uk/
You never know, they might be happy for the OP to do the donkey work chasing out, lifting floor boards etc, and price accordingly.
As for specifying the cable size blind….well, 6mm might do it, but it wouldn’t be you that lives with the consequences if it doesn’t and burns out.
And as it’s Essex, when they want to upgrade to a 10 oven small nuclear reactor and use that as a cooker instead, they might find that the 6mm cable can’t handle it and have to start ripping into walls again…think of all the damage that that would do to the gilt / gold edge tiles & Jimmy Saville style décor. :p
And last but not least, where has the SWA come into the equation.
Ah I just read back, it’s the master of the mandolin and finger chopping chef LLL hehe…it looks as though it wasn’t cooker size but the route they took to get there, round the outside of his house.
:p