There was an additional Episode 9 reviewing information that had come to light following the 'concluding' Episode 8. Interesting that a major sewer ran under the building. There was also mention of rat poison during the series but no discussion of any noises made by rats. I once stayed in a caravan that had a ran trying to gain access by chewing its way up from below and it made s hell of a racket. It would also respond to human voices in that it would pause scrabbling and stratching if you shouted at it...! It was eventually despatched to rat heaven with the hand axe (not a pleasant experience).
The whole French prince thing was a bit too much for me, too. I struggle with it and yes, there is the perfume connection to the land the house was built on but that could very well have been known about locally already (my childhood village still had tales from the time of the Black Death being passed down from generation to generation...!).
But there have also been new witnesses to the poltergeist activity come forward and so I find myself back at square one. Personally, I believe there was something paranormal going on but it was probably distorted by human hand/s. The most encouraging fact to come out of it all is that modern technology has not killed the poltergeist: the presenter states he has been contacted by 'many' listeners who had had their own poltergeist experiences. However, he makes the pertinent point that today's media would not be kind to such witnesses and thus they stay quiet