No Nick I was trying to get 32A out of 2x16 sockets, from the answer given above dosn't seem to be a safe way to do this.
As for a smaller immersion, not really on, heating plus battery charger draw about 18-19 amps which I just about get away with on a 16A supply. Switching the charger off and puuting the imerison on uses about the same. Just annoying have to do this. ....suppose I could buy a lower wattage kettle and then I wouldn't need the heating off.
In summary with heating on can only have one other circuit on without tripping out.