One is to write to the roofer to get him back giving him 7 days min to respond. I don't think this is the best solution given the link above and the fact they are ignoring my mum and dad anyhow.
Two, we get an independent roofing report and claim back money as appropriate for the fault
You suggested, earlier, that the roofers were the ones in the BBC article, and these were jailed. I don't think they would be released, to fix a roof?