when you say frost has caused some external cracks what are you refering to? an existing render which has to be removed before the new is applied?
i thought that something like render is expensive, �35-�50 m2
why do you think the foundation needs underpinning?if the house has been around for 150yrs surely thats proof its stable
i think that the cost of your joist replacement is one the cheapest and easiest jobs to do, and new studding to the bathroom walls is easy and allows the possibility of a new layout
probably the only thing you dont mention is a rewire, this is a big project you,re taking on if it goes ahead. are you sure this is what you want to do,bearing in mind your lack of experience
the thing i agree with most is the moisture meter lack of credibility.they can be set off by the palm of your hand they are so sensitive