Maximum Power Rating

I have a new seperate cooker and hob, rated at 2Kw and 6.2Kw respectively. With a total output of 8.2kw, I would need a 45amp Breaker. However, I have read that you do not have to account for the total power output as you never operate at this level and as such you can reduce the theoretical output by 1/3. Is this true, if so could I use a 30 or 32 amp breaker for my appliances? If not and I use a higher rating breaker, eg 45amp, can I use the existing 6mm2 cable which I have in place? Thanks

Personally I'd change to 10mm2 cable (6mm2 will handle 40 amps) and a 45 amp mcb, go for the worst case scenario possible, better than possibly burning ya house down.

The word you are looking for is diversity, it assumes that as an electric cooker has stats that switch on and off all the time so not every thing will be on at the same time. How ever, i would be inclined to agree with scoby_beasley

Thanks chaps, another quick one...a lot has been written in these forums about wiring seperate hobs and cookers, but I still dont have clarity. Would this scenario be ok...

Wire the 6Kw hob into a cooker termianal switched by a double pole control unit, then spur from the contol unit to a seperate 13A fused connection unit for the cooker. This way both appliances can be isolated from one switch.

The other option that I have seen here is to have both applicances into the same cooker outlet, is their an issue here that the lower rated appliance is only protected by the higher fuse rating? i.e Is it ok to have a 2kW cooker drawing what in needs from a 32 or 45 amp circuit along with the hob? - thanks

I'm no expert, but I would have thought going for the spur with 13a fuse would be your best bet, as the 2kw draw needs under 9amps to run (watts/volts=amps). This way your smaller fuse would blow first if you hit any problems.
I stand to be corrected, just going on what I did 14 years ago when rewiring house and the leccy man was okay with it then, dunno whats happened with regs since then though.