We stayed in Mill Cottage in autumn 2007 and found it to be above average for a rented cottage.
The proprietors are happy to accept bookings by the night, so you're not restricted by the usual Sat to Sat rules (although, at the time we visited there was a 'get 7 nights for the price of 5' promotion).
We were greeted by a generous and delicious homemade cream tea, all set out in the well-equipped kitchen alongside enough milk, bread and butter for the first couple of days.
The cottage was clean and tasteful, with lots of DVDs available, lovely bedrooms and a great shower room.
It is within walking distance of Fowey town centre (as long as you don't mind the return trip being up hill all the way : ) and there is a gorgeous walk over the top of the hill from the cottage which takes you down to the Fowey estuary beside a little stream - complete with picturesque waterfalls.