The underpinning, along with all my work on this house is being controlled by LABC.Lol you seem to jack of all trades !!underpinning a house properly also requires skill
I look at everything as a process. I am a degree qualified engineer having worked for several years in manufacturing. Whilst I don't claim to have in depth knowledge about very much I have learned that a combination of knowledge, aptitude and skills brought on to many jobs can achieve the correct result.
If the skills are lacking one can do a certain amount to reduce the skill level needed for the job. There are loads of tools out there that aim to do exactly that.
In the case of the marble tiling I know that marble tiles will be less forgiving than ceramic or porcelain, so from the point of process I need to be ontop of my game.