Complex sentence: In so doing the combined company avoided an expensive charter as the otherwise surplus "Peveril" was owned by the Steam Packet, not leased and had just been released from charter on the Heysham-Belfast route.
Split into simpler sentences: In so doing the combined company avoided an expensive charter as "Peveril" was already owned by the Steam Packet, not leased. Previously "Peveril" had worked on charter on the Heysham-Belfast route.