Whilst we've been maintaining a budget and a rough cost plan since engaging with out Architects, it's only in the last week we completed a detailed breakdown of our build costs via a quantity surveyor.   We'd budgeted ~£250k to build this house (£225k with contingency) and yet we were quite stunned (as was our architect) when the surveyor estimated a whopping £400k! We were expecting ~£1500/m2, not an extra    You can see a breakdown of this below: