We did this ride from Penzance to Plymouth as a week’s holiday (with plenty of sightseeing) in 4 sections. There are ferries along the route, so this would not work as a continuous ride. First, Penzance to Falmouth, which was full of nice rolling countryside. Second day, we rode to Fowey, which was the hardest day, with loads of hills and views of the sea! We ate fish and chips at Mevagissey and swam in the sea at Pentewan (a beautiful and quiet beach). Next, a short but remarkably hilly ride over to Looe, with plenty of time for sightseeing afterwards. Finally we rode to Carsand and got the ferry to Plymouth. The final stretch around Rame Head is really beautiful.
Stats: 144km total distance.