Actually, while were at Kew for the Bank Holiday, we also visited Queen Charlotte's Cottage, which is only open at weekends and for part of the year.
She added an upstairs floor to make what was known as the picnic room, and the trellis decoration was done by Princess Elizabeth, one of the fifteen (not a misprint) children of the royal couple.
The downstairs room is lined with floral and other prints, like those table mats that people get as wedding presents.
When we visited, the staff were wearing quasi Georgian dresses, but they did not need to say a lot as there is plenty of information, and not that much to see. It is, however, free to enter, once you have paid to get into the gardens, and its position is delightful. It is surrounded by bluebell woods, and there are oak trees which I think were planted by the Mayors of the different London boroughs some years ago, but I can't find the reference.
There is much more detail about the Cottage and its history on Rachel Knowles' excellent website.