Hi,
Train to Penzance,
Day 1 - Bus to Praa Sands - Walk back to Penzance (plenty of Pubs, Hotels, Hostels, B&B)
Day 2 - Penzance to Treen Cliffs (Pub, B&B, Campsite)
Day 3 - Treen Cliffs to Cape cornwall (St Just - Hostel, Pubs & B&B or take Bus back to Penzance (or take bus following morning)
Great walks with great views!