Apart from the obvious lack of information re location, should you not have had an engineer signing off the work as it progressed? Peanuts=monkeys cliche rears its head yet again.
Would suggest that you consider employing an architect well versed in domestic housing. A civil/stuctural engineer unless he specialises in housing would not be as conversant with the issues you are concerned with. I am a civil/structural engineer by the way
Have your architect establish to your satisfaction whether or not DPC and whatever is properly installed. This will likely involve opening up some elements for inspection.If work is confirmed to be properly executed the cost of confirmation will be to your account. If not, cost of all remediation will lie with builder.
I would be surprised if a Professional Architect would not be checking such critical building elements if he was paid to do so.