One of the problems with anything like this is that it does distract and detract from the programme itself, even if only in a small way. This thread bears that out. In the last episode of Cranford Miss Pole and, I believe, Miss Forrester shot round a corner to avoid someone, and I missed what they then said because of the plastic drainpipe running down the middle of the wall behind them. Even if just one person believes as a result of this that there was plastic guttering, or melodeons for that matter, in the middle of the 19th century then I think that is regrettable. If you are going to do a period piece in a period setting then the historical adviser should make sure that there are at least no glaring anachronisms.