I am installing a Garden Spa. Need a 35 amp supply (10mm Twin and Earth). My existing c/u is 100 amp split load with 25mm tails. The RCD is 63 amp 30ma trip. I already have sauna (6kw), cooker and immersion heater on the RCD. The Hot Tub will overload this. Only have domestic lighting and freezer not protected by RCD. Though about putting in a second c/u with 63 amp RCD and 40 amp mcb just for Hot Tub. This would mean putting 100 amp junction box in the tails. Other alternative is to uprate existing RCD. Any suggestions as to best way forward?