Cant comment on launching sites etc. but see Geoff's site at:
I cruise in the area and can recommend you take a trip out round Land's End (on a calm day).
Quite spectacular. Go via The Runnel Stone Bouy and up to Longships Lighthouse. Take your camera and dont forget to wave to all the tourists visiting the vastly overpriced and tacky Land's End plastic village on the cliff tops.
If you go Lizard way, check your chart and give the western side a wide sea berth. You can go right in on the eastern side however, right under the old Lloyds signal station.
Further east, ware The Manacles.