At the same time as the broadband dropping my telephone line quality is awful,
Could you give us a brief description of "awful", please? For example, clicking, buzzes, hums, whistles, white-noise, echoes, rushing water-like noises?
The term "network fault" relates to problems with the underlying infrastructure -- the metallic pathway over which both the telephony and the broadband services are carried.
Have you performed a QLT (quiet line test)? If not, please do so and let us know the result.
Finally, from whom do you obtain your (a) broadband service (b) telephony service? Having seen mention of a
BT HH, above, I suspect that it is
Beattie who provides you with both services.