Yes - it was the usual in-house-celebrity-treatment - a bit like the sudden change with Anne Robinson on The Weakest Link as soon as it was the celebrity version - go easy on your colleagues, you never know if you might be asking one for a job some day...
I agree that 'Uncanny' can get a starry-eyed over celebrities, such as the episodes where celebrities chose their favourite episode but contributed nothing else. But this may be a directive from the commissioning editors that the show should feature 'names' rather than something Danny necessarily wants, especially given that his book features ordinary folk not looking for more media exposure. Remember, this isn't an independent podcast but a BBC production and he will have had to sell his product to them.
By the time the episode with Daisy May Cooper was broadcast she had moved out of that house and to the best of my knowledge it is no longer on the market so it has either been sold or returned to holiday let status. I did find what I am 99% certain is the house but I had I follow a series of clues and pore over maps of pre-Beeching railways, etc. Most people won't go to those lengths, therefore I feel we can discount attracting buyers as a motive.
Yes, she has always had a keen interest in the paranormal and has attended ghost hunting events and you could certainly argue she was primed to interpret any strange noises in the house as ghostly activity. As regards the other experiences:
1. The Roman soldier sighting was by the housekeeper who "thinks she is a medium" and probably knew the Roman history of the area, so it will always be a weak one unless we hear it in the housekeeper's own words.
2. The hot tub is close to the lake itself and so the man seen outside near it may have moored a small boat thinking it was a different property or some other reason and then departed across the water before they got outside to investigate. Or, he may have been on the deck of a boat pulled up alongside and not actually on the property, but from her father's viewpoint sitting indoors it appeared as if he was on the decking. Finally, he may have been staff. But, as ever, we weren't there and he was...
3. The "whisper" in the upstairs room could have been wildlife, the wind, the timbers settling... That is, not a strong one.
4. The paintings on the wall being taken down is definitely hard to explain, although it was experienced by the housekeeper and not Daisy which would add an element of doubt except that according to Daisy it was two different housekeepers at different times
5. Hearing someone on the stairs when alone in the house is a familiar one to us Forteans and hard to explain but skeptics will point to it being a wooden building next to water.
6. The legs wearing white PE shorts without an upper body that is both seen and heard by Daisy is truly high-strangeness and what makes the episode so compelling. Skeptics will argue she was lying on the bed at the time and so was it a daydream? Yet she heard the feet pounding on the wooden floor which strongly suggests she was awake. Such a shame the child wasn't older and able to back up her experience. This one is definitely unexplained and it isn't as if Daisy needs the publicity when her career is doing so well. Rather, she is an 'Uncanny' listener like us and wanted to share her baffling experience.