We visited the beautiful Glendurgan gardens a week ago. This was our second visit. The gardens are truly awesome. It is a very hilly garden, but there are plenty of benches to sit, rest and enjoy the flora.
If you visit in the Summer season, there is a small boat which takes passengers from Helford to Durgan, thus avoiding the longish drive if coming from the Lizard. Parking for the ferry is in a large car park at the top of Helford village. You disembark at the bottom of Glendurgan and can access through a gate. The National Trust has a couple of cottages by the side of the river here, which look lovely, but look to be very expensive to rent.
I would thoroughly recommend a visit to this garden.