I didn't join BIA until June 79 so this was a little before my time, however chaffed hydraulic pipes were an ongoing challenge, the problem area as I remember were the hydraulic lines that ran forward of the wing front spar to the nacelle, these powered the retraction jacks, sequence valves, brakes and gear door jacks, these used to chafe through with wing vibration, due to the length of the individual pipes replacement was a challenge so inline repair inserts were fitted, this made the problem worse due to the congested areas.
For an aircraft of this size the hydraulics were very complex, as well as leaks "rapid cycling" was a common problem, this was caused by internal component leaks which prevented the system from maintaining full pressure without a constant pressure supply, the main culprits for internal leaks were thermal relief valves and door jack actuators.
The F27 pneumatic system was far simpler, however was prone to freezing if the water drains were not religiously drained.