The experience you've had with the Amish buying English farms and homes is very similar to my own. No gutting of houses or buildings, save the couple I am aware of where the copper wiring got stripped, everything else was left intact. I have never been in one with indoor running water, but many still have toilets, sinks, and tubs all hooked to the septic and they just carry in the water to fill them. The waste water still goes right into the septic tank. We have many that operate old tractor(up on blocks) driven sawmills and even some that will run a string of 6 volt light bulbs in their milking area.
As far as the stereotypes goes, you are absolutely correct and while it is no excuse, the demographics makes them easy targets. In the big picture, they are not really a very large community at all and the fact that they live in relatively localized pockets in large numbers(like Lancaster Co), there are enough bad ones concentrated in those small areas that those stereotypes seem to overwhelm the community, fair or not. The Amish are very much like the Native American community and the stereotype that they are lazy, stumbling drunkards, which I know first hand couldn't be further from the truth. I sit right across the hallway from a member of the Ho-Chunk Nation and he is one of the hardest working, most dedicated, family men I have ever met. He can bench press 425lbs, has about 7-8% body fat, his kids get straight A's and are dedicated martial arts students, and he manages his money well enough that his wife can stay home. Surely not your stereotypical "Injun" by any means. Again, not right and very unfair to the community as a whole, but very easy targets nonetheless.