I live in a concrete house. Only found out on the survey that it was non standard construction. There are broadly speaking 2 types of concrete house construction. Single skinned and double skinned. Then they were either made from concrete panels that were pieced together or done in a single pour with rebar throughout. We have a double skinned concrete house that was built in 1951, it was poured in one go and has rebar all the way through. Our estate was originally built for the MOD and then were all sold off privately. We had zero issue whatsoever getting a mortgage but there are some lenders which wont accept your application but these are the less mainstream ones like sainsburys or Newbury building society. We and our neighbours have got mortgages with Santander, Natwest, halifax, Lloyd's and Scottish widows that I know of and we never had a single issue applying.
That said if the house is single skinned and the type where the panels were pieced together run a mile as these are not mortgagable.
Best thing about my house is the energy bills are quite low as the concrete holds in heat in the winter and is cool in the summer. Also hanging anything on the walls is a bloody nightmare but once you put something up it will stay there for a hundred years!