single phase 100a and 2x 10.8kw heaters will not end well. your almost at your max 100a load just on the 2 heaters. switch on a kettle and your over 100a. switch on a few more things and chances are you will be in the dark until DNO come and replace the fuse... which they wont be happy about if it happens often
have you got the last page of the EIC, schedule of tests?
have you got the last page of the EIC, schedule of tests?