I am putting wiring in to a grade 2 listed building for a new kitchen.

I need to get 3 circuits past an aga to a kitchen island. I can't disturb the original flagstone flooring.

Sockets, 1 double and one socket socket at counter height, end of radial circuit

13 amp oven (based on manufacturers recommendation)

20 amp induction hob (based on manufacturers recommendations, has option to reduce.)

I could go in front of the aga as it's slightly raised but it's going to look unsightly and could actually be warmer than the back.

The aga is in a very large open fire place and I could drill through the side of the fireplace to run cables at the back, the back seems quite cool, especially at the bottom, I need to measure but would guess about 30 deg C.

Some numbers below

What do you think about the overall concept, do you have any experience with aga's, is it reasonable to assume the rear temperature won't exceed 50 C. (there is no back boiler involved)

There is a thermal cut out connected to 7 or 8 meters of sensor tube behind the aga, don't know what it's cut out point is at the moment

I am thinking of running all the circuits in 90 C thermosetting

 sockets on 4mm radial  

13 amp oven on 2.5mm radial

20 amp induction hob on 4mm radial

cable ratings, in free air, say 50 C ambient, 

2.5 mm 36A, @50 C = 29A

4.0 mm 49A  @ 50 C = 40A

6.0 mm 63A @ 50C = 51A

at 50 deg C Ca is 0.82 

Its a 3 or 4 inch gap at the back, did think about considering it like conduit but air is free to rise and take heat away, but even if I did the cable rating is still ok.