I assume you're talking about UK to UK calls (01 or 02 numbers).
If so, I'd not bother with a free E&W or 'free' 24/7 calls package provider but would opt for using 1899, 18185 or 18866 - 5p connection and talk as long as you like. I'd suggest a fit-program-and-forget
Orchid V2 LCR dialler to automatically insert the 18185 code for every outgoing call.
Problem there is if the person concerned has more than a single phone socket in use - they'd need a V2 for each.