The problem with switch mode power supplies is they can induce a larger current into the CPC due to the filtering capacitors and will cause issues with residual current protective devices and nuisance tripping. Under the 18th regs look up BS7671 Reg 531.33.2 which essentially states that the maximum earth leakage on each RCD must not exceed 30% of the nominal value, so your 30mA RCD's must not have more than 9mA. To achieve this might require additional RCBO's to spread the leakage so more cost to the consumer and more expense with equipment for the electrician.