Ofcom regs highlight not to repeat calls within 72 hours
Sounds like you are in danger of being fined by Ofcom for Persistent Misuse of the Telecoms network.
If you are working of manual lists it sounds like you have no control over how frequently you are calling. In general you should not attempt to call for a period of 72 hours after you made the last attempt.
Look up the redial rules from Ofcom.
Here is a summary of what I found.
\"In appropriate cases, Ofcom will take account of the extent to which any misuse is repeated. Generally, we are likely to regard repeated misuse in respect of the same number, or recipient, as an aggravating factor indicating a higher degree of harm.\"
\"One of the ways we may assess this is whether any calls constituting misuse are made within the 72 hours following the first instance of misuse.\"
Please be careful as the fines can be considerable.