If for some reason you do stop in Newlyn, visit Jelbert's Icecream shop ( right hand side of the road from Penzance). This small family owned business is open during the summer and during most other holidays. The home-made clotted cream icecream is out of this world. You can even ask for an extra topping of home-made clotted cream, which then freezes to a delicious crust on the top.
One tip; if you are buying a few icecreams then it is worth buying a small pot of clotted cream to share rather than an individual dollop on top of your cone. You can also ask for clotted cream to be sent to any address in the UK from here with an extra charge for posting and packaging.
Newlyn Pilchard Works is a living working museum. They are the only producers of salt pilchards, most of which are exported to the Mediteranean countries; in particular Italy - and use traditional wooden barrels and salt presses. I haven't tried salt pilchard yet, but it is supposed to be similar to salted anchovies. You can buy some to try if you visit.
The Pilchard Works is open from Easter to the end of October