Thanks for your reply.
Since this morning, the phone line has gone completely dead apart from a very few crackles.
Broadband is completely dead as well - this coincided with the activation of G.INP today. G.INP activated, 3 minutes later the broadband lost sync and phone went dead.
Sky said they have got BT to send a fibre SFI engineer out to take a look. I am assuming they are able to fix the phone line together as well since the proper function of both seem to be linked.
Over two weeks since I first reported the problem so fingers crossed it gets sorted soon.
Sky Fibre Max 80/20 - sync 62500/19999 around 450m (G.INP disabled 08/06/17 due to line fault)
Prev ISP Hx: Freeserve 48k > Wanadoo 56k > Tiscali 8mbps > TalkTalk 40/10 > Plusnet 80/20 > VM 200/20 > Plusnet 80/20