Hello Daniel and welcome,you have asked in a very polite manner about your conclusions about an installation after doing this course
Your gut feeling and your thoughts on loading exceeding mcb capacity seem probable with the information given to you
mcb ratings for the type of circuits you suggest seem to be correct
I presume that you would not be considering doing this work just yet,because of your admitted lack of experience and are asking for opinions to further your understanding
Take a look at the install and confirm what you have been told
Assess the loading and inspect the current set up with consideration being given to modifying the existing or installing extra capacity which will depend on 131.8 brb being satisfied, procedures for compliance with building regs also to be followed